THE POSSIBLE WAY OF INTRODUCING MINERAL ELEMENTS OF LIQUID HUMAN WASTES INTO THE MATERIAL CYCLE IN BIOLOGICAL LIFE SUPPORT SYSTEMS

摘要

Along with the atmosphere, water and food regeneration processes in biological life support systems it is important to provide units and links responsible for utilization of unused plant biomass, human wastes and returning, if possible, the most of wastes into the intrasystem material cycle. The experience on construction of biological life support systems (BLSS) gained by the Institute of Biophysics SB RAS (Krasnoyarsk, Russia) allows us to suggest constructing an integrated biological-physical-chemical life support system with the biological unit predominating. It is possibly to partially mineralize urine and solid wastes by "wet incineration" by hydrogen peroxide in electric field. We suggest decomposing urea by a urease-enzymatic method using soybean or canavalia flour containing sufficient amount of urease. Consumption of 1.5 g of flour for decomposition of urea in daily urine and the possibility of producing flour from soybeans and canavalia grown inside the system make this method of urea decomposition rather prospective. Further ammonia distillation using the nitrification unit and evaporation of solution would make possible to return nitrogen and water back into the intrasystem cycle. Probably, in long-duration space expeditions the utilization of urine would be confined only by extraction of nitrogen and water from urine with further removal of dry residue to the stock, as the problem of returning sodium chloride into the intrasystem cycling has not been solved yet. As all biogenic elements contained in urine (except nitrogen) get lost at that, the solution of the problem with introducing NaCl and mineral elements into the cycle with the help of halophyte plants Salicornia europaea are of sufficient interest. This work presents the experimental results of growing Salicornia europaea on model solutions containing biogenic elements in the amounts equivalent to their content in urine and on urine, which undergone physically-chemically treatment by peroxide and ammonia distillation after urease-enzymatic decomposition. Taking into consideration that the mineral elements content in urine can vary, 2 variants of model solutions were used. In the first variant the content of P was 8-fold, S - 7-fold, K - 8-fold higher than in Knop's solution; the content of Ca and Mg almost complied with that in Knop's solution. In the variant P was 12-fold, S - 17-fold, K - 17-fold, Ca - 6-fold and Mg was 8-fold higher than in Knop's solution. The content of N and NaCl in both variants was the same and constituted 0.18 g/1 and 10 g/1 respectively. The results of carried experiments showed that growing plants on urine treated in the above-mentioned way is possible; though the productivity of plants would be less than on model solutions. The reasons of plant productivity drop and the possible ways of their removal have been discussed.