Anaerobic Stabilization of Early Planetary Base Ersatz Wastewater Formulation

The challenge of effective nitrogen removal with a low Equivalent System Mass remains a goal of long-term manned space mission research. Ultimately, efficient organics removal followed by novel nitrogen removal processes will be advantageous compared to conventional fully-aerobic or anoxic-aerobic treatment systems. To date, the majority of research investigating the treatability of Early Planetary Base (EPB) ersatz wastewater formulations has involved the use of aerobic and anoxic treatment processes. However, little work has been published on studies done under strictly anaerobic conditions. In this work, a laboratory-scale anaerobic sequencing batch reactor (SBR) was fed EPB ersatz for 110 days. Initially, the reactor exhibited instability and biomass washout, with chemical oxygen demand (COD) removal of 22.7% ± 9.3%. After reseeding with new biomass, providing a supplementation phase, and increasing the SBR cycle duration from 6 hours to 12 hours, COD removal improved to 48.9% ± 10.8%. This performance was statistically different from the previous phase (P=0.004), demonstrating that longer cycle times favored increased organic removal. The supplementation period, during which the biomass was able to adapt to soap-based wastewater, resulted in more stable operation and prevented immediate biomass washout. Ammonia increased in the reactor effluent, due to conversion of organic nitrogen to ammonia. While COD removal performance was lower than expected, results suggest that anaerobic pretreatment is viable for increasing the nitrogen to organic carbon ratio of the wastewater, an important consideration for potential downstream nitrogen removal processes.