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Recent designs of water reclamation systems have differed on how to best utilize biological reactors. Some designs call for the bioreactors to be placed upstream of the distillation units, while other designs put the bio-reactors after the distillation units. The results from these two designs indicate that both designs are effective, but that each fulfills a different role. Specifically, small-scale applications which include ship-board systems or small bases should have the distillation unit before the bioreactor. Larger systems such as more complete land or space based facilities need industrial-scale water reclamation processing and should have the bioreactor before the distillation unit. A process design for each case is described and presented.

Modular biological reactor systems have been designed to remove trace organic contaminants and bacteria from recycled water in a low-gravity environment. The use of energy efficient biological treatment allows for the removal of trace organics using only oxygen and nutrients. Three separate reactor systems are currently in use. One reactor removes aromatics, one removes halogenated hydrocarbons and the third removes aliphatics from water streams. A different bacterial consortium is used in each of the three reactors. These reactors have been used to remove ethylene dichloride from a feed stream. The reactors were able to remove over 96% of the ethylene dichloride from a 50 ppm feed stream with a 24-hour retention time. Tests were also performed using kerosene and lubricating oil as contaminants in a reactor feed stream. The immobilized bed reactors removed over 99% of the contaminants from the feed using a 12 hour retention time.

A series of experiments was performed to test the viability of using immobilized-bed, biological reactors to remove trace organic contaminants from recycled water. Protoype reactors were designed and built to test this concept on three groups of target organics, aliphatics, aromatics, and chlorinated aliphatics. Three experiments have been performed using phenol as the target compound. Phenol was fed to the reactor in a 100 parts per million (ppm) phenol in water feed and 10 ppm phenol feed. The 10 ppm feed experiments were run with the reactors operating in recycle mode, which allows the reactor to operate as a continuously stirred tank reactor (CSTR), and in plug-flow mode. The 100 ppm experiments showed an average phenol removal efficiency of 99.98% over a seven day period, with an average retention time of 27.2 hours. The seven day 10 ppm experiment in recycle mode had a 97.08% removal efficiency with a retention time of 13.7 hours.