**2.4 Nalgonda technique**

The Nalgonda technique is a modified coagulation protocol, which was developed by National Environmental Engineering Research Institute, Nagpur, India [35]. It takes advantage of the synergy between precipitation using lime and alum flocculation to facilitate F adsorption on Al(OH)3 flocs formed in the solution [36]. The F adsorbed is removed with the flocs by sedimentation. The Nalgonda technique has now been introduced in many countries but it requires high doses of flocculants leading to large sludge transfers and it may release excess Al3+ into the treated water [37].
