Evaluation of short-term anaerobic fermentation using bioflocs waste and performance assessment

Abstract

Excessive bioflocs are becoming a novel challenge to the development of biofloc technology (BFT). The present study assessed the viability of utilizing short-term anaerobic fermentation as a potential technique for the reclamation of bioflocs waste (BW). According to the different composition of fermentation substrates, the experiment was divided into: a group fermented with BW only (BG), a group fermented with the mixture of BW and straw (BSG), and a group fermented with the mixture of BW, effective-microorganism products (EM), and straw (BESG). Our results indicated that the contents of total potassium (TK) and organic matter (OM) were improved through 30 days fermentation, and the highest TK (1.3 g·100 g−1) and OM (53.4%) were both found in BESG. However, the fermentation process altered the microbial structure of the original bioflocs and reduced microbial diversity. The highest abundance of representative microorganisms of fermentation such as Clostridium_sensu_stricto_1 sp., and Ureibacillus sp. were detected in the BG group, and the obvious ammonification process was also detected in the BG. The final germination index (GI) values ranged between 98.8%-113.7% and all fermented products met the criteria for fertilizer maturity since day 20th. The application of fermented products was tested through the pot experiment with Brassica rapa L. chinensis, and the highest fresh weight (14.1 g) and yield (312.6 g·m−2) were found in the group with BG fermented products. However, a prominent improvement in Brassica rapa L. chinensis' quality had not been found. Overall, the anaerobic fermentation improves the quality of the original bioflocs, and the addition of fermented products based solely on the BW can significantly increase plant yield.