Lab scale study on electrocoagulation defluoridation process optimization along with aluminium leaching in the process and comparison with full scale plant operation

摘要

An excess or lack of fluoride in drinking water is harmful to human health. Desirable and permissiblenstandards of fluoride in drinking water are 1.0 and 1.5 mg/L, respectively, as per Indian drinking waternquality standards i.e., BIS 10500, 1991. In this paper, the performance of an electro-coagulationndefluoridation batch process with aluminium electrodes was investigated. Different operationalnconditions such as fluoride concentration in water, pH and current density were varied andnperformance of the process was examined. Influence of operational conditions on (i) electrodenpolarization phenomena, (ii) pH evolution during electrolysis and (iii) the amount of aluminiumnreleased (coagulant) was investigated. Removal by electrodes is primarily responsible for the highndefluoridation efficiency and the adsorption by hydroxide aluminium floc provides secondary effect.nExperimental data obtained at optimum conditions that favored simultaneous mixing and flotationnconfirmed that concentrations lower than 1 mg/L could be achieved when initial concentrations werenbetween 2 and 20 mg/L. pH value was found to be an important parameter that affected fluoridenremoval significantly. The optimal initial pH range is between 6 and 7 at which effectivendefluoridation and removal efficiencies over 98% were achieved. Furthermore, experimental resultsnprominently displayed that an increase in current density substantially reduces the treatmentnduration, but with increased residual aluminium level. The paper focuses on pilot scale defluoridationnprocess optimization along with aluminium leaching and experimental results were compared with anfull-scale plant having capacity of 600 liter per batch.