Title: Coagulation process for fluoride removal by comparative evaluation of alum and PACl coagulants with subsequent membrane micro-filtration

Authors: Madhu Agarwal; Swati Dubey; A.B. Gupta

Addresses: Department of Chemical Engineering, Malaviya National Institute of Technology, Jaipur, 302017, India ' Department of Chemical Engineering, Malaviya National Institute of Technology, Jaipur, 302017, India ' Department of Civil Engineering, Malaviya National Institute of Technology, Jaipur, 302017, India

Abstract: In this paper, the fluoride removal efficiency of the two coagulants was compared in batch and continuous mode. The optimum dosage for PACl was 438-2,410 ppm and 275-1,510 ppm for alum for treating fluoride concentrations of 2-10 ppm. The results showed that PACl was equally effective in bringing the fluoride level within the acceptable limit (1.5 ppm) in water with half lime dosage, compared to alum. Residual fluoride in dissolved form was found to be 0.66-0.83 for alum and 0.78-0.99 for PACl. It was also observed that residual aluminium decreases from 0.46 (alum) to 0.34 (PACl) for 4 ppm of initial fluoride concentration. After subsequent microfiltration, residual Al was found to be 0.182 ppm (alum) and 0.143 ppm (PACl). From the results, it can be stated that the residual turbidity and TDS for alum, as compared to PACl. Thus, switching the process to continuous mode using PACl coagulant with a sequential microfiltration, could meet quality criteria for drinking water.

Keywords: alum; de-fluoridation; fluoride removal efficiency; coagulation technique; polyaluminium chloride; sweep floc; bridging action; membrane.

DOI: 10.1504/IJETM.2017.089650

International Journal of Environmental Technology and Management, 2017 Vol.20 No.3/4, pp.200 - 224

Received: 30 Sep 2016
Accepted: 20 Aug 2017
Published online: 05 Feb 2018 *

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