Biologically Mediated Solids Degradation and Nitrogen Recovery from Inedible Plant Residues 1999-01-2065

Nutrient recovery and biodegradation of inedible biomass is an integral part of an Advanced Life Support (ALS) system for space travel. This study investigates the mineralization and nitrogen recovery of hydroponically grown crops, namely, tomato, peanut, wheat and a 50:50 mixture of peanut and wheat. Shaker flask studies were conducted under various growth conditions of temperature and incubation times utilizing activated sludge and Phanerochaete chrysosporium (P. chrysosporium) inocula. Incubation temperature ranged from 25°C to 60°C and the flasks were monitored for nutrient recovery and solids reduction at 16, 32, 64 and 128 days. For the activated sludge systems, overall solids destruction during the 128 days of incubation ranged from 56% to 60% for the crops investigated. Similar results were found for the fungal systems indicating no substantial degradation enhancement. Incubation temperature had a minimal effect on total solids reduction but appeared to influence the leach-ability of certain nutrients. Recovery of nitrogen (as NO₂^--N and NO₃^--N) was high for both the activated sludge and the fungal systems indicating that final effluent contains sufficient amounts of nitrogen for hydroponic plant growth. Although substantially reduced during treatment, chemical oxygen demand (COD) of leachate remained at levels that may inversely impact hydroponic growth of plants and may require further reduction. During the shaker flask studies, it was determined that most of the solids destruction occurred within the first 16 days of incubation. The extent and rate of nitrogen release and COD uptake during the initial stages of incubation were studied in two separate batch reactor experiments, one with tomato and the other with a 50:50 mixture of peanut and wheat.