Automated Closed Loop Control of Ozone Disinfection Using Flow-Paced Off-Gas Measurement

摘要

Ozone disinfection is an environmentally attractive alternative to chlorine because of the lack of a toxic residual, its excellent virucidal properties, and its reduced potential to form hazardous constituents in the treated effluent. It is, however, energy and capital intensive relative to chlorination, and for this reason it has not been widely accepted yet in the U. S. municipal market. Any method that would reduce the operating cost of ozonation would accelerate its acceptance in that market. In this paper the authors report an automated control strategy that, when implemented at treatment plants with a daily average flow greater than 8000 cu m/d, will result in a substantial savings in the electrical cost of production. The method consists of a flow proportional signal and an ozone concentration signal that combine to control the feed gas flow to and the power setting of the ozone generator according to fluctuations in liquid flow and ozone demand. The concentration signal is measured in and transmitted from the off-gas from the ozone contractor. They present an annualized cost comparison of this approach with existing strategies in use today and report a savings of $7,000 to $15,000 per year for a hypothetical treatment plant with a daily average flow of 23,700 cu m/day.