Abstract: An oxidation chamber used for irradiating an incoming liquid containing unwanted organic pollutants has a structure that facilitates automatic self-cleaning at intervals. A modular construction is used, and three basic types of modules are employed. One of the modules is a TEFLON.RTM. lined carbon steel pipe through which a shuttling scraper is forced at intervals. The shuttling scraper includes an annular wiper that simultaneously cleans the inside surface of the surrounding tubular module as well as the outside surface of an enclosed quartz tube. The annular wiper sealingly engages the quartz tube and the tubular module so that it is driven like a piston by the full pressure of the liquid. When the shuttling scraper has reached the end of the tubular module, it parks itself in a position that causes only minimal pressure drop.