Water Technology - Jan 2012
FEATURE 22 Water Technology January 2012 should Youll save yourself time hassle and money WT Heather Rekalske is a technical writer for the Myron L Company a privately held company whose core is researching and developing effective and innovative solutions for the water quality industry Myron L manufactures a broad spectrum of water quality instrumentation including reliable cost effective monitor controllers as well as precision digital and analog handheld meters The most exciting new development in the handheld line is the FCE function which accurately measures free chlorine using accelerated ORP readings Why ORP ORP is a faster simpler empirical measurement than titration with DPD or other methods and in many cases it gives the most accurate picture of the effect of all oxidizing and reducing chemicals in solution No in depth knowledge or training is required to obtain accurate repeatable results User error is virtually eliminated because ORP readings require no subjective visual interpretation nor do they require calibration Using ORP disinfectant control can be automated because the measurement produces an electrical signal that can trigger switches when outside established control parameters And ORP sensors are relatively low maintenance If youre not using ORP to monitor and control chemical additions that work through REDOX you on the sensor and the particular context for safe bathing water In the disinfection of drinking water an ORP value of 800 mV is required for oocyst inactivation For the purpose of pretreatment screening to detect chlorine levels prior to contact with chlorine sensitive RO membranes influent must first be screened to determine which chemicals besides chlorine are present that contribute to the ORP value With these interferants characterized and pH and temperature held constant ORP can be correlated to specific sanitizer concentrations such as chlorine in their known forms Some manufacturers of RO membranes and other water quality treatment equipment will also specify an ORP tolerance value for prescreening and influent control The same holds true of effluent screening Circle 216 Circle 217
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