Presence of fluoride in drinking water leads to serious effects on human. Fluoride in traces promotes dental health. On excess amounts causes serious effects on humans such as crippling bones and discoloration of teeth. There are some techniques for the removal of fluoride in drinking water to control these effects.
Defluoridation is the process of removal of fluoride from water. This technique is expensive. During the process of removing fluoride, accumulation of unnecessary toxic sludge in the drinking water. It may cause some health hazards but it can be controlled by taking proper care while processing. Defluoridation process is divided into three basic types depending on the mode of action.
- Based on chemical reaction with fluoride
- Based on adsorption process – activated charcoal, processed bone
- Based on ion exchange process – anion and cation exchange resins
Techniques for the removal of fluoride from drinking water (defluoridation) include:
- Reverse osmosis filtration: Reverse osmosis filtration is used to remove fluoride from bottled water. So most of the bottled water contains no fluoride. This technique is unaffordable for personal use. In this hydraulic pressure is applied to the concentrated solution to counteract the osmotic pressure. Thereby pure water is separated from the concentrated solution and collected at the bottom stream of the membrane.
- Activated alumina defluoridation: These filters are used by locale where fluoridation in water is prevalent. These filters are relatively expensive and need to change frequently. It is a better option for home based removal of fluoride from drinking water. In this process, alumina is processed to create pores on it. Then it attracts the fluoride atoms present in the water and forms a large mass. Finally it can be separated from pure water by distillation or sedimentation process.
- Distillation filtration: It is one of the defluoridation technique for the removal of fluoride from drinking water. These are commercially available distillation filters that can be bought to remove fluorides from drinking water. This technique is reliable, advanced and efficient method for removal of fluoride from water. In this process, fluoride drinking water is taken into the distillation apparatus. Water is heated to form vapor. As the vapor is passed into the condenser, the flow of cooling water reduces the temperature of the vapor and forms liquid droplets. This pure water is separated from the residue and can be used for drinking purpose.
- Electrolysis: The principle involved in the electrolysis process of defluoridation is adsorption. This process does not require addition of chemicals. In this, fluoride is precipitated with the freshly prepared aluminum hydroxide which is generated by the anodic dissolution of aluminum ions in electro chemical cell. The advantage of this process is it occupies less space and consumes less energy. It does not need any pre and post treatment.