Domesticating Chlorella vulgaris with gradually increased the concentration of digested piggery wastewater to bio-remove ammonia nitrogen

Abstract

Digested wastewater derived from anaerobic fermentation of livestock manure contains lots of inorganic nitrogen (N) and phosphorus (P). It would cause water pollution and waste of resources if discharged without purification. Microalgae are desirable media for waste nutrients treatment for its high growth rate and lipids content. However, due to the characteristics of high ammonia nitrogen and low C/N ratio, it's hard for the original Chlorella vulgaris to removal N and P in the digested piggery wastewater. Hence, Chlorella vulgaris was domesticated with gradually increased digested piggery wastewater concentration (from 20% to 100% (v/v)) to resist high ammonia nitrogen (678 mg/L) and other pollutants. After 5 cycles of domestication, Chlorella vulgaris cultivated in the 500 mL closed bioreactor could remove ammonia nitrogen and total phosphorus in the raw digested piggery wastewater at a rate of 71.4 mg/L/d and 1.63 mg/L/d, respectively. Moreover, almost 100% of the NH4+-N (678 mg/L) and TP (20.8 mg/L) in the raw digested piggery wastewater could be removed by the domesticated microalgae cultivated in a 64 L open raceway pond. These results confirmed that environmental domestication was an optimal choose to get microalgae species that suitable for digested piggery wastewater treatment.