Limewater Pretreatment In The Re-mineralization Process

This topic is mainly focused on the pretreatment of the limewater in the industry of re-mineralization.The content of this project includes the following fields:(1) The impaction of the turbidity of the mineral water due to the usage of limewater with different levels of turbidity;(2)Research about the results of the variation of the limewater's turbidity with using different types of filtration treatment;(3) Research about the affect of the limewater's turbidity with using the limewater-precipitation or the combination of the precipitation and filtration;(4) Investigation about the stability and safety of the product with using the limewater.The core of the re-mineralization is to improve the quality of the water by using the carbon dioxide,saturated limewater which could help to improving the calcium hardness,alkalinity, and the pH value of the water. There are two ways of using the limewater based on stage dependent:one is to use it in the flocculation basin stage; and the other one is to use it in the clean water tank stage(after filtration).To minimizing the affect of the increasing turbidity by adding the limewater into clean water, the implement of the researches about the direct filtration, precipitation, and combination of both the former and latter treatment is necessary. According to these researches, there is no impaction to the product when using the density of 5 mg/L pre-treated limewater within the turbidity of 15 NTU;increased turbidity of 0.3 NTU due to the using of the turbidity of the limewater in a range of 15 to 50 NTU; and increased turbidity of 0.5 NTU with using the turbidity of the limewater in a higher range of 50-110 NTU.As decreasing the quality, the effect of limewater turbidity will also slightly decrease.According the results of the filtration testing,it is better to put the filtration treated limewater into the clean water tank to have a low and stable turbidity of the product.However the problem of the direct filtration treatment is its short filtration period.The organic-filter-materials filtration would achieve the adsorption to the cal vital which could cause an intense decreasing of the saturation of the limewater and consequently decreasing of the alkalinity. Furthermore,as the deterioration of the filter-materials with 2 hour-period-using tank after one month,more acid is required for the acid cleaning-one unit volume of carbon is immersed into 3 unit volume of 1 mol/L hydrochloric acid with 10 minutes stirring. According to the limewater precipitation tests,the precipitation time for vertical flow sediment basins is 1 hour arid the inflow limewater fraction is 0.15%.The turbid degrees of limewater is 650-900 NTU and the effluent turbidity is 50-100 NTU. The stirring with center pipe and flocculate has little effect to the effluent turbidity. After the upgrade of the device,enlarging the upper part of the center pipe to 100L mixing chamber in order to mixing and mixing flocculation experiment. The flocculation mixing has good effect for fluid of limewater precipitation, which slightly reduces the effluent turbidity of fluid of limewater.As adding the limewater, the water resistance,LSI,AI,CCPP will increase and RSI,LR will decrease which illustrate that the water resistance,corrosion decrease and the corrosion tumors penetration of anions decreases,so the chemical stability of water will increase.The yearly average additive adding in the front is 6-7mg/L,when quality adding at rear equals and grater than 3mg/L, besides the Larson ration between 0.66-in0.62 which can be smaller than 0.5,the other water chemical stability index can be reached the acceptable numerical range.