Integration of anaerobic digester with oxidation ditch-membrane bioreactor as a zero organic waste system for building application

Abstract

The objective of this study is to study the efficiency of organic substance removing in anaerobic digestion system and oxidation ditch membrane bioreactor (OD-MBR) for managing liquid digestate and wastewater sludge to completely zero organic waste. The process can be done by digesting food waste from the canteen with sludge from OD-MBR with the proportion of 10:1 by weight and liquid digestate from anaerobic digestion process will be further treated by OD-MBR to study the productivity of methane and efficiency of waste treatment. This study is a semi-continuous experiment by adjusting the experimental conditions for six conditions, as follows; HRT of 24, 18, and 12 hours at the water velocity of 0.3 and 0.6 m/s with 28 days per condition. The result shows that the combined system has high efficiency of waste treatment and the total amount of produced biogas is 167.63 Nm3 along the experiment. The highest amount of biogas of 34.92 Nm3 is from the experiment using a HRT 24 hours and water velocity 0.3 m/s (SC1). The highest specific methane yield of 1.12 m3CH4/kg VS removed. For the efficiency of waste treatment, the range which COD can be treated is 85.44-93.77%. TKN is 64.31-85.57%, Nitrate is 40.82-54.17%, and phosphorus is 44-51.17%. In the term of net energy balance the result show that net energy balance is negative in every experiment. However, when considering the energy saving, for combined system Experiment 1, (SC1) can save LPG the most or 4,428 THB/year. The evaluation by LCA with SimaPro 8 software for global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP) shows that the combined system between AD and OD-MBR has the GWP of 1.29 kg CO2 eq. per FU, AP of 0.0128 kg SO2 eq per FU, and EP of 4.659 kg PO4 eq per FU.