Biochemical methane potential (BMP ) assay to evaluate methane production in the sludge from a swage treatment plant in Rio de Janeiro, Brazil

Abstract

Biochemical methane potential (BMP) is defined as a measure of substrate biodegradability
determined through the cumulative CH4 production from a sample anaerobically
incubated and monitored over the time. The BMP assay is widely used to test the
anaerobic degradability of different organic waste. However, due to the lack of a
standardized protocol, the BMP assay presents serious limitations that limit its
application by the industry. The reliability of the information generated by these assays
can be questioned due to the influence of specific experimental and operational
conditions and the way data is presented. The objective of this study was to implement
and describe a replicable and low cost methodology for BMP evaluation using anaerobic
sludge (AS) from a wastewater treatment plant (WWTP). Anaerobic sludge (AS) from the
WWTP operated by the State Company of Water and Wastewater (CEDAE), located in the city
of Rio de Janeiro, Brazil, was collected to assess the potential for methane production from
sludge in BMP bioreactors developed on a laboratory scale. The experiments were carried out
in six replicates at 37±1°C and manually stirred. The sealing system developed was suitable for
the experiment proposal. The sludge feeding the bioreactors presented the following physicalchemical
characteristics: pH (7.4-7.6), alkalinity (2.382 g CaCO3 L-1), CODi (21.903 mg L-1),
TS, TVS and VSS (4.8%, 2.5% and 1.5% respectively). The bioreactors showed cumulative
methane production ranging from 124 to 143 mL after 11 days, indicating the reproducibility
of the system. The discrete changes in pH and alkalinity during the experiments could be
indicative of the microbial community stability during the process. The results showed that
the methodology for the construction, calibration and operation of the bench reactors were
replicable.