Microbial Nitrification in the C.R.O.P. - Biofilter

Abstract

The Combined Regenerative Organic food Production (C.R.O.P.) - biofilter is a waste management system that utilizes microorganisms to recycle biological waste products such as human urine into an aqueous fertilizer solution rich in nitrate. It has been designed to enable higher plant cultivation without the need of soil during future manned space exploration. The aim of this study was to investigate if the microorganisms inhabiting the filter are responsible for the nitrification in the filter. Two experiments were conducted to test this hypothesis. During the first experiment, the pH of the usually acidic filtrate was raised to test the biocenosis adaptation and analyze if the nitrification processes are influenced. Shifts in populations of nitrification-associated bacteria were observed and changes in nitrification affinity detected. For the second experiment a sterile filter unit was set up to investigate if nitrite is converted to nitrate chemically in the acidic filter solution. Nitrite accumulated in the filter, indicating that no chemical nitrification took place. These results demonstrate that nitrification only occurred in the presence of microorganisms in the C.R.O.P. - filter. Furthermore, it was shown that nitrifiers are present and adapted to the environment present in the biofilter.