A novel approach using protein-rich biomass as co-fermentation substrates to enhance phosphorus recovery from FePs-bearing sludge

Abstract

A novel approach for the enhancement of phosphorus (P) recovery from Fe bound P compounds (FePs)-bearing sludge by co-fermentation with protein-rich biomass (PRB) is reported. Four PRBs (silkworm chrysalis meal, fish meal, corn gluten meal, and soya bean meal) were used for co-fermentation. The results revealed that PRBs with strong surface hydrophobicity and loose structure favored the hydrolysis and acidogenesis processes. Sulfide produced by PRB could react with FePs to form FeS and promote P release. Due to the neutralization of volatile fatty acids (VFAs) by a relatively high concentration of ammonia, the pH was maintained near neutral and thus prevented the dissolution of metal ions (e.g., Fe and Ca). This was beneficial to save the cost of subsequent P recovery and form high-purity struvite. Compared with the control, the soluble orthophosphate and VFAs increased by 88.3% and 531.3%, respectively, in the co-fermentation system with silkworm chrysalis meal. Cysteine was the important intermediate. The metagenomics analysis indicated that the gene abundances of phosphate acetyltransferase and acetate kinase, which were key enzymes in the acetate metabolism, increased by 117.7% and 52.2%, respectively. The gene abundances of serine O-acetyltransferase and cysteine synthase increased by 63.4% and 54.4%, respectively. Cysteine was primarily transformed to pyruvate and sulfide. This study provides an environment-friendly strategy to simultaneously recover P and VFAs resources from FePs-bearing sludge and PRB waste.

Keywords: FePs-bearing sludge; anaerobic co-fermentation; mechanism; protein-rich biomass; struvite; volatile fatty acids.