Study On Stability And Health Of Mineralized Two-stage Reverse Osmosis Desalted Permeat

In our country,due to the lack of fresh water,people turned to the sea to get water resources.Reverse Osmosis(RO)has become the most widely used technology in seawater desalination because of its advantages.However two-stage RO desalinated seawater is soft water which lacks calcium,magnesium and other mineral ions.Moreover it is acidic with low pH value and poor stability.During the process of desalinated seawater transportation,pipe network would be corroded.Therefore mineralizer is added to improve water quality.In this work,standard for drinking water and mineral water was studied and drinking water quality was investigated to provide theory support for mineralizing.In order to know the relationship between the dosage of mineralizer,stability and health,the ratio of mineralizer was studied and indicators(pH value,calcium content,magnesium content,alkalinity,hardness),stability index(Ryznar stability index,Larson index,Calcium carbonate precipitation potential),health index(Oxidation-Reduction Potential,Cerebral haemorrhage incidence rate health index)and taste index were measured.(1)After studying Standard for drinking water and mineral water and measuring water quality indicators,in order to obtain the index evaluation system of mineral water.Then three groups of mineralizer:?CaCO3,MgCl2,NaHCO3,?CaCl2,MgCl2,NaHCO3 and ?CaCl2,MgCl2,NaHCO3,KHCO3 were selected to be used in subsequent experiments.(2)Under this experimental condition,when using mineralizer CaCl2,MgCl2 and NaHCO3,study had shown that IR values decreased and they were close to 6.0?7.0 with the increase of HCO3-dosage from 50 mg/L to 90 mg/L,and then increased and were far away from 6.0?7.0 with the increase of NaHCO3 dosage from 90 mg/L to 110 mg/L,meaning that water stability got better and then got worse respectively.CCPP values decreased with the increase of NaHCO3 dosage and water quality stability changed from precipitation tendency to solubility tendency.When the concentration of NaHCO3 reached 70 mg/L,CCPP values leveled off,so did water stability.With the increase of the amount of NaHCO3,LR decreased and water stability improved.With the increase of the amount of NaHCO3,ORP first decreased and then began to level off when the amount of NaHCO3 reached 90 mg/L,which means that the health of water increased first and leveled off later.Therefore the optimum amount of NaHCO3 was 90 mg/L.IR and CCPP values decreased and water stability decreased with the increase of CaCl2 dosage.LR values increased with the increase of CaCl2 dosage,meaning that water stability got worse.With the increase of the amount of CaCl2,ORP increased,which means that the health of water decreased.Thus the appropriate amount of CaCl2 was 20 mg/L.Replacing some NaHCO3 with KHCO3 in this study was more beneficial to people's health and water taste improvement.(3)After mineralizing,the stability and health of water were improved obviously.When mineralizing,with the increase of HCO3-dosage,the ORP value decreased.According to its index value,the water quality was healthier.ORP values decreased by about 20 mV for every 20 mg/L HCO3-dosage increase from 50 mg/L,70 mg/L to 90 mg/L.When the amount of HCO3-was constant,with the increase of potassium salt that replaced sodium salt,ORP values decreased and the water became healthier.After mineralizing,due to the high content of sodium ions,the health index of the incidence of cerebral hemorrhage was lower than 5.2 mg/L,which was detrimental to health.When some of the NaHCO3 was replaced by KHCO3,with the increase of KHCO3 ratio,the health index of the incidence of cerebral hemorrhage value was closer to the judgment value of 5.2 mg/L.Therefore increasing KHCO3 content ratio was more beneficial to health.When the dosage of CaCl2 is 50 mg/L,MgCl2 is 15 mg/L,HCO3-is 50 mg/L(K:Na=1:1),mineral water's health index of the incidence of cerebral hemorrhage value reached the standard.According to taste index,most of the mineralized water tasted good.Water that was mineralized with KHCO3 was better than that without KHCO3..