AWWA WQTC65851

This poster presentation highlights the quality assurance and quality control programs currently implemented at Passaic Valley Water Commission in Totowa, New Jersey to ensure continued optimal performance of dissolved ozone monitors. The monitors are used to determine the primary disinfectant residuals at the Little Falls Water Treatment Plant. There are a total of four ozone contactors at the facility with four monitors installed in multiple cells of each contactor. The program success requires the efforts of the Laboratory, Operations and Maintenance Departments and is the primary focus of a designated online water quality Instrument Team at the facility. In order to comply with 40 CFR 141.74, the PVWC Laboratory holds state certification for Standard Method 4500-O₃ B Ozone Residual, Indigo Colorimetric Method, where this method is used to verify the calibration of all of the continuously monitoring ozone sensors that are in service at a required frequency of twice per week. The PVWC Laboratory staff also incorporate an additional step in the method to determine the amount of interference resulting from the oxidation of existing manganese in the water. The amount of interference can than be accounted for and corrected, ultimately increasing the accuracy of the method. This is of particular importance since many systems have converted from pre-chlorination to ozone and do not necessarily remove manganese before the ozone process. The presence of manganese would give a false positive ozone residual using the Indigo Colorimetric Method. The Operations Department has been trained by the Laboratory to perform daily ozone residual checks using the Hach AccuVac method. The spectrophotometer used for this procedure is performance checked weekly by the laboratory. The operation department's results are reviewed by the instrument team daily to determine if there is an issue. The instrument team is responsible for troubleshooting. The Maintenance Department corrects any flow-related problems resulting from sample line clogging. The Instrument Team has implemented a preventive maintenance program for the dissolved ozone sensors that is designed to avoid sensor failure. Quarterly, each sensor is refurbished and zeroed according to the manufacturer's procedures. Includes tables, figures.