Abstract

VILLEGAS-MENDOZA, Iván Emmanuel; MARTIN-DOMINGUEZ, Alejandra; PEREZ-CASTREJON, Sara  and  GELOVER-SANTIAGO, Silvia Lucila. Electrocoagulation to Remove Silica from Cooling Towers Water. Tecnol. cienc. agua [online]. 2014, vol.5, n.3, pp.41-50. ISSN 2007-2422.

This paper presents the results of a study carried out about the effect of water quality on the removal of dissolved silica using an electrocoagulation process with aluminum electrodes. Silica is found in replacement water (RW), usually known as make up water, and in cooling tower blowdown water (CTBW). Tests were conducted on a small pilot scale (~2 lmin^-1) with a continuous flow device. The treatment train consisted of electrocoagulation (EC), flocculation, sedimentation and sand filtration. Two distinct RW and two CTBW with different physicochemical characteristics were studied. The response variables analyzed were: efficiency of aluminum to remove silica (ratio mgl^-1 of dosed Al³⁺/mgl^-1 SiO₂ removed), removal efficiency of dosed Al³⁺, hydraulic head loss throughout the electrochemical reactor and voltage. The cost of the treatment for the four types of water is discussed. The ratio mgl^-1 Al³⁺ dosed /mgl^-1 silica removed ranged from 1.09 ± 0.06 to 1.33 ± 0.05 when treating RW and 0.85 ± 0.1 when treating CTBW. The consumption costs of energy, chemicals and electrodes for RW treatment ranged from US$ 0.52 to 0.74 m^-3, and was approximately US$0.53 m^-3 for CTBW.

Keywords : Aluminum; blowdown; cooling tower; electrocoagulation; make-up; silica; water quality; concentration cycles.