Ultraviolet irradiation and chlorination dechlorination for municipal wastewater disinfection: Assessment of performance limitations

A large-scale ultraviolet (UV) disinfection system was operated in parallel with an existing full-scale chlorination system for comparison of process performance at a 340 L/s (7.8 mgd) municipal wastewater treatment facility. The UV disinfection system was operated using two different lamp configurations: vertical and horizontal. Both UV system configurations were operated at the same hydraulic loading, corresponding to the loading at anticipated peak flow for the facility. Both UV systems were shown to be capable of achieving effective inactivation of coliform bacteria. The chlorination system yielded inconsistent performance, probably as a result of inefficient contact chamber design. The major limitation to performance in the UV system was fouling of lamp jackets. Chemical analysis of the fouling materials revealed the presence of a broad spectrum of metals in an amorphous precipitate. Fouling control by air sparging was shown to be effective in slowing the fouling process. An economic analysis of the two disinfection alternatives revealed that UV irradiation would be a less expensive alternative than chlorination and dechlorination at the West Lafayette Wastewater Treatment Plant, both in terms of capital and operating costs.