Role of spent coffee ground biochar in an anaerobic membrane bioreactor for treating synthetic swine wastewater

Abstract

Using anaerobic membrane bioreactors (AnMBRs) to treat swine wastewater is an effective method to recover bioenergy. However, due to the inhibitory effect of high concentrations of organic matter and ammonia nitrogen on microbial activities in swine wastewater, some problems are evident such as low recovery efficiency and serious membrane fouling. In this study, biochar prepared from spent coffee grounds (SCG-BC) was added to AnMBR to investigate its effect on the operation process. Results reported that methane yield rose from 0.227 LCH4/g-CODremoved to 0.267 LCH4/g-CODremoved along with a reduction in CO2 being produced at 35.25 % after adding SCG-BC. It confirmed that in-situ biogas upgrading was achieved. As well, the total volatile fatty acids declined to a low concentration of 194.87 ± 51.82 mg/L while pH remained steadily at 7.70 ± 0.31. Adding SCG-BC reduced irreversible membrane fouling by 34.69 %. Microbial community analysis showed that SCG-BC increased the relative abundance of methanogenic archaea, especially Methanosarcina (from 1.47 % to 8.03 %). Also, Anaerolinea and Methanosaeta participating in direct interspecies electron transfer were enriched onto biochar. They acted together to enhance the biogas production. It can be concluded that AnMBR with SCG-BC addition has good application prospects in recovering bioenergy from wastewater.