Raceway pond cultivation of a new Arthrospira sp. ZJWST-S1 in digested piggery wastewater treated by MBR and ozonation

A new Arthrospira strain named Arthrospira sp. ZJWST-S1 was isolated from a local digested piggery wastewater (DPW) storage pool in Jiaxing City, Zhejiang Province, China. It possessed good stain resistance against contaminants in DPW, which was pretreated with a membrane bioreactor (MBR). The strain was identified as Arthrospira platensis (A. platensis) based on its morphological characteristics and the 16S rDNA sequencing analysis. The effect of chrominance on growth of A. platensis ZJWST-S1 was investigated in a field raceway pond filled with MBR effluent or MBR effluent decolorized with ozonation. After ozonation, the chrominance of MBR effluent was decreased from 700 mg Pt/L to 150 mg Pt/L. Two runs of cultivation showed that A. platensis ZJWST-S1 grew faster in the ozone decolorized MBR effluent, the averaged biomass concentration being 0.907 g/L after 10 days of cultivation, close to that in a Zarrouk medium (0.969 g/L). By comparison, the biomass grew much slower in the non-decolorized MBR effluent (0.624 g/L). The pollutant removal was also benefited from the accelerative growth of A. platensis ZJWST-S1 in the decolorized MBR effluent. Almost all ammonium, 61.2% of nitrate and 68.1% of phosphate were removed by the A. platensis ZJWST-S1 in the decolorized MBR effluent, much higher than the corresponding values of almost all ammonium, 25.4% of nitrate and 36.5% of phosphate in the MBR effluent. Furthermore, the Arthrospira biomass harvested from the ozone decolorized MBR effluent after 10 d cultivation was with crude protein content of 59.1%±3.5% in dry algae powder. The content of Pb, As, Cd and Hg in biomass was also low enough to meet the Chinese Arthrospira Standard for Animal Feed (GB/T 17243-1998). This study showed that the new strain A. platensis ZJWST-S1 possessed potential to be used for producing animal feed and simultaneous removal of nitrogen and phosphorus in DPW.