[Removal of excess fluoride from water plants by poly aluminum chloride as a new coagulant]

ABSTRACT

The fluoride ions are commonly found in water resources. These ions should be in optimum levels for prevention of dental caries. However, the excess value can cause such health problems as fluorosis. The aim of the present study was to investigate the removal of excess fluoride ions by using poly aluminum chloride as a new coagulant that is used in water treatment plants. All experiments were conducted in batch system. Several combinations of parameters such as initial fluoride concentration [1.4, 2 and 2.4 mg/L], pH of solution [3, 7, 9], poly aluminum concentration [10, 20, 30, 40 mg/L], and exposure time [30, 60, 90 minute] were investigated. Various concentrations of poly aluminum chloride solution at different pH levels were added into 200 ml of fluoride solution, and samples were taken in predetermined time intervals and the final concentration of fluoride was determined by spectrophotometer at 570 nm. The results showed that, the highest removal was obtained at pH=7. In addition, it was observed that fluoride removal efficiency was higher in pH=5 than in pH=9. Also the results showed that, removal efficacy can be increased by increasing the poly aluminum chloride and the exposure-time. This study denoted that removal of high levels of fluoride ions can effectively be done by using poly aluminum chloride as a new coagulant. Its use is possible in water treatment facilities without any need for modification in water treatment plans