Effects of hydraulic retention time and organic loading rate on performance and stability of anaerobic digestion of Spirulina platensis

Abstract

© 2016 IAgrE. The effects of hydraulic retention time (HRT) and organic loading rate (OLR) were investigated during a continuous anaerobic digestion of Spirulina platensis. The continuous process operated with varying HRT (10-25 d) and OLR (1.0-4.0 [g VS] l-1d-1) resulted in the biogas and methane yields in the range of 0.276-0.502 l [g VS]-1and 0.163-0.342 l [g VS]-1, respectively. The methane yield decreased with the increase in OLR and the reduction in HRT. Maximum methane yield of 0.342 l [g VS]-1was produced when the digester was operated at OLR of 1.0 [g VS] l-1d-1and 25 d HRT. A mathematical model was developed from a kinetic study for predicting methane yield as the function of HRT during a continuous digestion. The model performed well at OLR lower than 2.0 [g VS] l-1d-1, at which the digestion was not limited by high ammonia levels or volatile fatty acid accumulation.