Enhancement of Taihu blue algae anaerobic digestion efficiency by natural storage

Abstract

Taihu blue algae after different storage time from 0 to 60 d were anaerobic fermented to evaluate their digestibility and process stability. Results showed that anaerobic digestion (AD) of blue algae under 15 d natural storage led to the highest CH4 production of 287.6 mL g(-1) VS at inoculum substrate ratio 2.0, demonstrating 36.69% improvement comparing with that from fresh algae. Storage of blue algae led to cell death, microcystins (MCs) release and VS reduction by spontaneous fermentation. However, it also played an important role in removing algal cell wall barrier, pre-hydrolysis and pre-acidification, leading to the improvement in CH4 yield. Closer examination of volatile fatty acids (VFA) variation, VS removal rates and key enzymes change during AD proved short storage time (≤ 15 d) of blue algae had higher efficiencies in biodegradation and methanation. Furthermore, AD presented significant biodegradation potential for MCs released from Taihu blue algae.

Keywords: AD; AK; AMPTS; Automatic Methane Potential Test System; Biogas production; CH(4) production rate; Chl-a; Enzymatic characterization; ISR; MCs; Microcystins; Natural storage; P; P(max); PHA; R(max); SEM; TAN; TC; TCD; TFA; TKN; TN; TP; TS; Taihu blue algae; VFA; VS; acetate kinase; anaerobic digestion; chlorophyll a; cumulative specific methane yield; inoculum to substrate ratio; lag phase; maximum CH(4) potential; microcystins; polyhydroxyalkanoate; scanning electron microscopy; thermal conductivity detector; total Kjeldahl nitrogen; total ammonia nitrogen; total carbon; total nitrogen; total phosphate; total solids; trifluoroacetic acid; volatile fatty acids; volatile solids; λ.