Chemically and biologically driven carbon transformation flow in MSW leachate treated by a high-solids anaerobic...

Carbon transformation is important for an anaerobic process but is often overlooked when using an anaerobic membrane bioreactor (AnMBR). Material flow in an AnMBR treating calcium-rich MSW leachate was thus quantitatively investigated to illustrate how chemical and biological factors affect carbon transformation. The results show that a remarkable amount of carbon in the leachate was degraded, with 50.1% of it should be converted into CH₄ and 37.7% of it into CO₂. However, a much smaller value of 40.6% and 14.2% were experimentally obtained. Chemical analysis indicated that the precipitation of calcium carbonate captured 1.23 g/day of carbon. At the same time, about 23.2 g/L HCO₃^- and 16.6 mg/L CH₄ (both as carbon) were dissolved in the liquid. Those features facilitated the high CH₄ (74%) content in biogas. A carbon transformation model was therefore established and showed carbon flow into the gas, liquid, and solid phases, respectively. Carbon existed in biogas, permeate, and discharged sludge was also obtained.