Devising a means to solve this problem by removing H2S requires the cooperative efforts of engineers and microbiologists. It is well recognized that phototrophic bacteria, especially purple nonsulfur bacteria (PNSB) are well capable of treating wastewaters due to their versatile metabolic pathways. They have a capability to grow as both photoautotrophs and photoheterotrophs under conditions of anaerobic or microaerobic-light, and chemoheterotrophs under conditions of anaerobic or aerobic-dark [5,6,7,8]. Some members of the PNSB such as Rhodopseudomonas, Rhodobacter and Rhodospirillum are known to reduce the H2S odor from facultative waste stabilization ponds [9, 10].