The tests were carried out by WRK Design and Services Limited, an independent chemical engineering consultancy specialising in contract research and development and pilot plant studies. They were conducted at the Lightwaves Leisure Centre in Wakefield.
The main objectives of the trial were to analyse swimming pool water samples for TOC, THMs, active/free chlorine and TDS (total dissolved solids) before and after the installation of a UV water treatment system.
In all cases, there was a significant reduction of TOCs, THMs, combined chlorine and TDS post-UV. Transmission* values were higher post-UV, indicating a reduction in suspended organic material (with correspondingly lower absorbance) as a result of UV. The lower combined chlorine levels also indicated lower levels of organic material, matching the higher transmission values. Chlorine reacts with organic material to form combined chlorine, so lower organics would result in less combined chlorine, lower absorbance, and therefore higher transmission.
Following the trial WRK concluded that, “The results of the analysis indicate that the medium pressure UV system at Lightwaves Leisure Centre was beneficial in reducing the TOCs and THMs to very low levels (~ 25 µg/litre) up to 14 days after installing the UV system.” The report also confirmed the reduction in combined chlorine was also significant.
* The condition of the water being treated will determine how well the UV light passes through it (UV transmittance).