Patent ID: 7261821

Claim:
An automated process for treating a contaminated aqueous system with an aqueous solution of chlorine dioxide generated by a chlorine dioxide generator having a reaction chamber, wherein contaminated water enters the chlorine dioxide generator and is motive dilution water for precursor chemicals that are reacted in the reaction chamber of said chlorine dioxide generator, such that said motive water exits the chlorine dioxide generator as an aqueous solution of chlorine dioxide, which is fed into the contaminated aqueous system to be treated, wherein said process comprises: (a) pre-selecting: (1) a concentration of chlorine dioxide for the aqueous solution of chlorine dioxide exiting from the reaction chamber of the chlorine dioxide generator, and (2) a generation efficiency for the chlorine dioxide generator; (b) monitoring: (1) a total system water demand of the contaminated motive dilution water entering the chlorine dioxide generator; (2) the pH of the aqueous solution of chlorine dioxide exiting the reaction chamber of the chlorine dioxide generator, (3) the amounts of precursor chemicals, (4) the concentration of chlorine dioxide in the aqueous solution exiting from the reaction chamber of the chlorine dioxide generator, and (5) the generation efficiency of chlorine dioxide generator; (c) calculating: (1) the total chlorine dioxide demand needed for the contaminated motive dilution water entering the chlorine dioxide generator in order to obtain the pre-selected concentration of chlorine dioxide in the aqueous solution of chlorine dioxide exiting the reaction chamber, and (2) the amount of precursor chemicals needed to treat the contaminated motive dilution water entering the reaction chamber of the chlorine dioxide generator in order to obtain said pre-selected concentration of chlorine dioxide in the aqueous solution of chlorine dioxide exiting the reaction chamber of the chlorine dioxide generator; (d) adjusting the amounts of precursor chemicals to maintain: (1) a pH of 2.0 to 3.0 for the aqueous solution of chlorine dioxide exiting the reaction chamber of the generator, (2) the pre-selected concentration of chlorine dioxide in the aqueous solution of chlorine dioxide exiting the reaction chamber of the chlorine dioxide generator, and (3) the pre-selected generation efficiency of the chlorine dioxide generator; (e) feeding the aqueous solution of chlorine dioxide exiting from the chlorine dioxide reaction chamber into said contaminated aqueous system, wherein the steps of said process are automatically carried out by a Programmable Logic Controller (PLC) containing a mass flow feed forward algorithm that automatically regulates the amounts of the precursor chemicals pumped into reaction chamber and a feed back algorithm that regulates the concentration of chlorine dioxide in the aqueous solution of chlorine dioxide generated.