Poole " Waste Water Treatment Plant " AKA " the sh*t works installed a load of those. Very powerful UV tubes inside a polycarbonate protective outer. Of course like all things they have a specific life span before they need changing. Disconnect power, unscrew the end of the outer protective tube, slide out the UV lamp and replace. Hang on a minute, who built that wall there? It's too close to the ends of the tubes to be able to replace them 🤔😁anyway - eventually they installed a UV thingy to kill all the bugs and it was OK after that
