AUTOMATION OF THE COAGULANT DOSAGE FOR FLOTATION SYSTEMS USED FOR THE POST-TREATMENT OF THE EFFLUENT OF ANAEROBIC REACTORS

Abstract

This work was focused primarily on the establishment of appropriate parameters for automated dosing of ferric chloride as a function of the turbidity of the effluent from an Expandable Bed Anaerobic Reactor (RALEx) that was post-treated in a dissolved air flotation system. Initially, experiments were conducted on a small scale for obtaining the relation between the parameters most suitable dosage of turbidity and ferric chloride. The data resulted in a nonlinear equation, however a linear fit was done in order to allow the insertion of the curve in the dosing pump that requires data in this format. Later the equation obtained was used to automate the coagulant dosage sent to the dissolved air flotation pilot unit (DAF), by means of the signals obtained from a continuous flow turbidimeter that was installed at the inlet of the flotation system. At the end of the experiments it was possible to check the good operational control of the RALEx/DAF system provided by this automatic coagulant control system based on the turbidity of the anaerobic reactor effluent, thus resulting in a good quality final DAF effluent which showed average values of turbidity equal to 25 NTU, SST equal to 22 mg/L, DQOB equal a 59 mg/L and P-PO43- equal a 0.8 mg/L. Keywords: automation, continuous flow, dissolved air flotation, anaerobic reactor bed expandable.