| Groundwater is an important source of urban water supply.Groundwater can reach the "Drinking Water Health Standards"(GB5749-2006),but its high hardness and high alkalinity may cause scale problems in the process of boiling drinking water.Drinking boiling water is an important characteristic of residents in our country.Users complained groundwater water system from the senses and health concerns.A large number of residents bought household water purifiers or bottled water for solving the problem of scales.Scale problems become one of the problems that domestic water supply enterprises face and urgently solve now.Based on the mechanism of scale formation,this paper put forward the principle of scale removal by acid-alkali balance aeration method and established the scale removal process.Experiments were studied in a county water plant in Shaanxi Province,and its groundwater was used as raw water.Based on the feasibility of scale removal in the laboratory experiment,two sets of shallow(pool depth of 1.2m)aeration device were designed and processed,whose treatment scale was 50 m3 / d.In order to further reduce the area occupied by the process,the deep(height of 5.5m)aeration device whose treatment scale was 100 m3 / d was designed and processed.After a year of field parameter optimization and continuous operation test,the main parameters of the process were obtained,and the reliability of the process and the safety of the water quality were verified.The water plant scale removal process plan was put forward.(1)The results showed that the removal rate of the scale was more than 90% when the dosage of the scale inhibitor which used strong acid as the main component was 0.14 ‰/L and the ratio of gas to water was 1: 6 in the scale inhibitor with strong acid as the main component.After boiling water turbidity would from 5.0 or more NTU down to 1.0 NTU below.The pH of the incoming and outgoing water is essentially the same.The removal of scale is determined by the addition of scale inhibitors.With the increase in scale inhibitor's dosage,scale's removal rate increased.The pH of the effluent is determined by the ratio of gas to water.The ratio of gas to water increased then the pH of the effluent increased.(2)The results showed that deep and shallow aeration had no significant differences with regard to the addition of scale inhibitors for scale removal.But in the same conditions about gas to water ratio,the deep aeration test had higher pH.Gas to water ratio of 1: 4 can make the same pH of inlet and outlet water.The packing layer can reduce the gas to water ratio to 1: 3.The filler layer is the best for 30 cm from the aeration head.(3)Stable continuous operation test showed that the effect of the system effluent scale is stable.Water quality analysis report showed that water quality qualified.The addition of the scale inhibitor and aeration did not affect the water quality safety,but increased the concentration of anions in the water supply and the total dissolved solids.There were no significant differences in the decontamination process for water supply and taste.(4)The water plant scale removal process plan was put forward.The scale of the water supply is 20000 m3/d.Mixing tank,aeration tank and blower room should be built.The structures should be arranged which combined with the existing layout of the water plant.The new structures cover an area of about 250m2. |
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