LAUSR

The hydroxyl radical (·OH) scavenging capacity is a useful parameter for the design and operation of an advanced oxidation process in water treatment. The scavenging capacity may change with time, and it would be useful to continuously measure this change to be able to optimize AOP doses. In this study, we first reviewed current methods for scavenging capacity measurement to identify strengths and weaknesses of each. This information helped to guide the design of an external calibration method to allow straightforward laboratory and field measurement of ·OH scavenging capacity. The method used low-pressure UV/H2O2 as the ·OH generation system, methylene blue (MB) as the probe compound, and isopropyl alcohol (IPA) as the standard. By monitoring, offline, the colour decay of MB in a series of IPA solutions with different scavenging capacity, a calibration curve was established between the colour decay rate and the scavenging capacity. The measured colour decay in real water samples can then be used with this external calibration to estimate their scavenging capacity. Work was undertaken to ensure that the process would be robust under a wide range of water quality conditions. Parallel tests using this method compared to the benchmark methods confirmed its robustness and accuracy.