Study On Treatment Of Hardness Of Underground Water Source Using Lime Softening-Flocculation Process

With the socio-economic development in our country, people’s requirements ondrinking water are increasingly high. And that drinking water safety at rural areas is themajor concern of governments at all levels, and is an important indicator to reflect thesocio-economic development in rural areas Drinking water hardness is directly related tothe human body’s physical health, and the hardness will affect the normal life of the peoplewhenever is too high or too low.Combining hardness treatment researches of drinking water in recent years, thisthesis studied quality characteristics of groundwater in Liuhe water treatment plant,determined to choose lime softening—flocculation process, and used static jar test anddynamic pilot test, and the economic and technical analysis test process was also taken.Static jar tested the relationship between hardness and lime dosage and determinedthe lime dosage ranged from180to240mg/L, and PAC was selected as a coagulant andidentified its dosage ranged from15to30mg/L. Also affect of precipitation time andfiltration conditions on the test results was studied. Finally, being optimized by orthogonaltest, the optimal parameters were as follows: Ca(OH)2=220mg/L, PAC=20mg/L, and limereaction time=10mins, sedimentation time=30mins. With an integrated processing unit,Ithe pilot plant further explored the impact of the lime dosage and PAC dosage on theresults. It was proved that the lime softening process had obvious effect on hardnessremoval, because the hardness removal rate of static beaker test could be up to62%andranged55%to67%in pilot tests.Based on the infrastructure and equipment investment and the cost of wate, the paperalso carrid on economic and technical analysis both on the ion exchange process and limesoftening process. The results show that the technology infrastructure and equipmentinvestment of lime softening was1.46million RMBand higher than the ion softeningprocess, which was300,000RMB. While the lime softening process’s operating costwas1.334yuan/m3, and the ion softening process costed1.791yuan/m3;The ion exchange process has high hardness removal efficiency, but it cannot deal with the temporary hardness; while the lime softening process can remove HCO3-, whichessentially solve the problem of floating debris in the boild effluent.