The Use of Chlorella species to Remove Nutrients from Dairy Wastewater to Produce Livestock Feed

The goal of the study was to utilize Chlorella sp. to recycle nutrients from a dairy wastewater lagoon producing microalgae biomass for dairy cattle. Chlorella sp. was cultured in mixotrophic conditions with various ratios of raw dairy wastewater with a lab-scale (1.25 L) environment and a pilot-scale (70 L) environment. The influence of extra CO₂, pH, temperature, solar radiation, and photosynthetic active radiation were tested for cell growth, biomass productivity and nutrient (ammonium, nitrate, and phosphate) removal from wastewater. The objective of this study was to determine the alternative ratios (control, 1:10, 1:20, 1:30, or 1:40) of dairy wastewater, where Chlorella sp. biomass could be produced to remove nutrients. Additionally, the study evaluated the addition of CO₂ into the cultivation system to increase biomass yield. During the first experiment, the lab-scale and pilot-scale experiments showed similar biomass growth after seven days of growth. The control had the highest biomass, followed by 1:10. For the pilot-scale experiment, the treatments (control, controlN, 1:10, 1:10 N, 1:30, and 1:30 N) were different from each other for nutrient removal rates and biomass production. The bioreactors designed for this study may be used on farms to recycle dairy wastewater and produce enriched biomass for use to feed livestock.