Nutrient Recovery From Source-Separated Human Urine by Microalgae in Continuously Fed Raceway Pond

Abstract

Nitrogen and phosphorus are essential nutrients for all organisms and recovery and reuse of these resource are reasonable (Yuan et al. 2012). Source-separated urine is one important nutrient source. The aim of this study was to cultivate microalgae Scenedesmus acuminatus in 15 times diluted source-separated human urine in continuously fed outdoor raceway pond (2000L) in Nordic climate (Tampere, Finland) and evaluate biomass production and nutrient recovery. Highest biomass production with OD 1.4 and TSS 1.1 g/L was achieved. Efficiency of microalgal growth started to decrease when the temperature decreased below 25 °C (pH < 8.5). On average 26 % (2.7 – 51 %) of total nitrogen entered was captured by microalgal cells and 46 % (0 – 100 %) of total nitrogen entered was volatilized. On average 36 % (0 – 100 %) of the phosphorus entered was captured by microalgae or precipitated. Based on the results it could be concluded that microalgae can be used to recover nutrients from diluted source-separated human urine in open raceway ponds in Nordic climate conditions without addition of trace elements, artificial light or CO2.