In the water-treatment plants, the process of coagulation and flocculation has a special place and it has always been an effort to achieve high efficiency in this part of the water treatment with low cost. In recent years, extensive research has been carried out on the process of coagulation and flocculation, and various coagulants and flocculants materials have been investigated. The purpose of this study is the investigation of chemical coagulation and flocculation efficiency of different coagulants and flocculants (Aluminium sulfate, Bentonite, Iron(II) sulfate, Polyaluminum chloride, Poly-Ferric chloride, Sodium aluminate, Anionic polyelectrolyte and Cationic polyelectrolyte) in phosphorus pentoxide and fluoride removal in the phosphoric and acid water treatment plant. The present study - a pilot scale experiment- was conducted in the laboratory of water and wastewater chemistry of Kimia Daran Kavir factory in 2018. In order to compare the efficiency of coagulants and flocculants materials in removal of phosphorus pentoxide and fluoride, the experiments were performed based on the variables PH, EC, TH, TDS, particle sedimentation velocity, turbidity after 5, 10 and 30 minutes, size of particles formed and correlation of particles precipitated in the beaker bottom. At the end, the efficiency of each coagulants and flocculants materials was reported qualitatively in the removal of phosphorus pentoxide and fluoride. After preparation of the samples in the Jar test apparatus, rapid mixing for all experiments was 70 rpm for one minute, slow mixing was 10 rpm for 15 minutes and for 30 minutes to sedimentation in static conditions. The results showed that all of the coagulants reviewed in this study are not suitable for use in the phosphoric and acid water treatment plant of Kimia Daran Kavir factory. Cationic polyelectrolyte is a suitable flocculant for use in the phosphoric and acid water treatment plant of Kimia Daran Kavir factory. The use of lime in the phosphoric and acid water treatment plant, in addition to the role of the removal of phosphorus pentoxide and fluoride, plays a coagulant substance role. Therefore, there is no need to use a coagulant. Also, according to the particle sedimentation velocity, the best PH for cationic polyelectrolyte injection is PH = 11. Also, it can be concluded from the results of the above experiments that coagulants and flocculants do not play a role in increasing or decreasing the amount of TDS and TH.
