Re-cultivation of dry microalgal-bacterial granular sludge

Deepening the research on the storage and transportation of the microalgal-bacterial granular sludge (MBGS) will help its engineering application. Herein, re-cultivation of naturally dried MBGS was investigated. The results showed that the MBGS could be re-cultivated in 18 days in both aeration and non-aeration systems. Notably, the aeration system could facilitate granulation with superiority in both granule size and settleability of MBGS over the non-aeration system. The ammonia removal by re-cultivated MBGS under aeration condition was dramatically higher than non-aeration condition. In addition, the microbial community of MBGS had evolved dramatically after re-cultivation. Furthermore, the primary mechanism for the granule growth and the formation of new granule during the dry MBGS re-cultivation under aeration condition was deduced to be microbial coaggregation (e.g. Acinetobacter), whereas under non-aeration condition it might be ascribed to the microbial mobility. This study is expected to provide insights into the storage of MBGS and the restart of MBGS process. [Display omitted] •Re-cultivation of dried microalgal-bacterial granular sludge (MBGS) was studied.•Dried MBGS could be recovered in structure and properties within 18 days.•Aeration facilitates granular settleability, size and ammonia removal of MBGS.•Microbial community of MBGS had evolved dramatically after the re-cultivation.•The possible mechanisms for re-cultivation of dry MBGS were put forward.