1 research outputs found
Free Nitrous Acid (FNA)-Based Pretreatment Enhances Methane Production from Waste Activated Sludge
Anaerobic
digestion of waste activated sludge (WAS) is currently
enjoying renewed interest due to the potential for methane production.
However, methane production is often limited by the slow hydrolysis
rate and/or poor methane potential of WAS. This study presents a novel
pretreatment strategy based on free nitrous acid (FNA or HNO<sub>2</sub>) to enhance methane production from WAS. Pretreatment of WAS for
24 h at FNA concentrations up to 2.13 mg N/L substantially enhanced
WAS solubilization, with the highest solubilization (0.16 mg chemical
oxygen demand (COD)/mg volatile solids (VS), at 2.13 mg HNO<sub>2</sub>–N/L) being six times that without FNA pretreatment (0.025
mg COD/mg VS, at 0 mg HNO<sub>2</sub>–N/L). Biochemical methane
potential tests demonstrated methane production increased with increased
FNA concentration used in the pretreatment step. Model-based analysis
indicated FNA pretreatment improved both hydrolysis rate and methane
potential, with the highest improvement being approximately 50% (from
0.16 to 0.25 d<sup>–1</sup>) and 27% (from 201 to 255 L CH<sub>4</sub>/kg VS added), respectively, achieved at 1.78–2.13
mg HNO<sub>2</sub>–N/L. Further analysis indicated that increased
hydrolysis rate and methane potential were related to an increase
in rapidly biodegradable substrates, which increased with increased
FNA dose, while the slowly biodegradable substrates remained relatively
static