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Using Dairy Livestock Wastewater to Cultivate the Microalgae for Nutrient Recovery
1, 2 , * 1, 3 , 3 , 1 , 1 , 4 , 1, 3
1  Department of Environmental Engineering and Earth Sciences, Clemson University, South Carolina 29634, United States
2  Center for Synthetic Biochemistry, Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technologies, Shenzhen, Guangdong 518055, China
3  Biogeochemistry & Environmental Quality Research Group, Clemson University, South Carolina 29442, United States
4  USDA–ARS, US Arid Land Agricultural Research Center, Maricopa, Arizona 85138, United States
Academic Editor: Daniel Tan

https://doi.org/10.3390/IOCAG2023-17344 (registering DOI)
Abstract:

The increasing demand for animal products has triggered the scale-up from traditional household breeding to large-scale livestock farms with concentrated animal feeding operations (CAFOs), resulting in the production of a significant volume of livestock wastewater containing a large amount of nutrients and antibiotics. The improper management of this agricultural wastewater before discharge to surrounding freshwater ecosystems can easily deteriorate the natural environment. Here, we used the dairy livestock wastewater to cultivate the microalgae for nutrient recovery along with the surface water protection. We successfully cultivated two microalgae species of Chlamydomona reinhardtii and Chlorella protothecoides by using 100% dairy livestock wastewater [pH: 8.76 ± 0.04, conductivity: 6.57 ± 0.07 mS/cm, total organic carbon (TOC): 153 ± 5.54 mg/L, total nitrogen (TN): 298 ± 12.1 mg/L, PO43--P: 6.42 ± 0.79 mg/L]. We further investigated the microalgae growth and nutrient removal under 1000, 3000, 5000, and 7000 LUX with light on for 12 hours per day. OD680 showed a similar tendency between 5000 LUX and 7000 LUX, which were higher than those under 3000 LUX and 1000 LUX. OD680 under the same simulated sunlight intensity was similar between the two microalgae species. pH was significantly increased after the microalgae cultivation, without obvious variations among different treatments (i.e., light intensity and microalgae species). During the microalgae cultivation, we observed the consumption of 12-28% of TOC mass, 88-95% of TN mass, and 58-74% of PO43-P mass. Specifically, more than 99% of NH4+N mass was used for microalgae growth. We observed a significant decrease of SUVA254, indicating the aromaticity reduction of the wastewater after the microalgae cultivation. Total fatty acid content testing indicated C16:0, C18:1, C18:2 as the major fatty acids of C.reinhardtii and C. protothecoides, and their total fatty acid contents reached up to 13% and 17% by dry weight respectively. Our study concluded that the dairy livestock wastewater was successfully used to cultivate two microalgae species of Chlamydomona reinhardtii and Chlorella protothecoides for nutrient recovery as well as the potential biofuel production.

Keywords: Dairy livestock wastewater; microalgae; antibiotics removal; nutrient recovery

 
 
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