CONSIDERATIONS FOR SUCCESSFUL FULL-SCALE IMPLEMENTATION OF OZONE IN WATER REUSE APPLICATIONS

摘要

Success with full-scale ozone system operation, maintenance and performance requires cooperation among several parties and good implementation of many technical details. In this paper three details were selected as being especially important based on personal operating experience at >70 ozone installations. The topics are a) Keeping ozone generators dry; b) Foam control in the contactor head space and c) Automatic control focused on treatment performance. Ozone generators must be kept dry in order to operate efficiently and with little maintenance. Generators in many plants have operated for years without maintenance. Unfortunately, generators at some plants have required expensive maintenance within months or a few years. Well performing ozone generators are kept dry while in operation and during standby. Power applied to a wet generator creates nitric acid that leads to generator inefficiency, 'malfunction and premature generator cleaning. Methods to keep generators dry, dry and very dry are discussed in this paper. Unlike drinking water ozone systems, wastewater ozonation develops "foaming" conditions within theozone contactor head space. Foam control (e. g., spray nozzles) is used to prevent carryover into the ozone destruct units. If excessive foaming is projected, foam collection, removal and disposal might be considered. Ozone systems are designed to meet primary and secondary treatment objectives. Disinfection might be the primary objective and oxidation of endocrine disrupting compounds a close, secondary benefit. In this paper, disinfection performance that is measured by ozone - exposure "Ct" calculations (i. e., residual concentration times contact time) is discussed as the approach for feedback control of ozone dose. Disinfection performance measured by "Ct" was selected because drinking water ozone systems have been automated by this approach and a wealth of experience exists. Besides, ozone systems that operate with disinfection as the primary treatment objective typically achieve secondary, oxidation treatment benefits because "ozone demand" reactions are satisfied.