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A closed-loop, regenerative life support system must include a method for recycling organic waste materials. With a Controlled Ecological Life Support System (CELSS), this will be accomplished by decomposing the wastes and using the effluent to formulate a nutrient solution which supports food production by plants. The waste processing technology used may be either physicochemical or biological. Although the effluents from biological processors have been extensively evaluated as fertilizers for soil-based agricultural systems, few experiments have been conducted to evaluate their suitability in hydroponic applications. This paper describes the results of a series of experiments performed to evaluate effluent from an anaerobic bacterial reactor as a nutrient source for hydroponically-grown plants. Germination and initial seedling growth were found to be suppressed by pure effluent.

This paper describes the results of a project involving an anaerobic digestion system used in treating the human and vegetative wastes from a Controlled Ecological Life Support System (CELSS). The anaerobic digester biologically breaks down the organic matter in the wastes into a mixture of methane gas and carbon dioxide, while significantly reducing the BOD(biological oxygen demand ) of the wastewater. A standard waste was formulated consisting of a mixture of swine waste (the surrogate for human feces and urine), green wastes (primarilly lettuce), and paper wastes. The equipment used for this project was a 2.7 cubic meter digester tank filled with plastic media and heated to an average temperature of 35°C. The digester was run over period of 200 days and loaded on the average of five days per week. The results over this test period showed a 94% reduction in BOD and a 98% reduction in suspended solids in the wastewater.