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Jesъs Rodrнguez–Martнnez*, Josй A. Rodrнguez–de la Garza, Yolanda Garza–Garcнa
Kinetic assessment of the volatile fatty acids as a strategy
to maintain the sustainability of the biodegradation of chemical oxygen demand
of easily acidifying wastewater
Abstract
Kinetics of the production and consumption of
volatile fatty acids (VFA) such as acetic-, propionic-, butyric- acid and
alcohols during anaerobic digestion of model wastewater was studied under
different concentrations of sorbitol (g/l) as carbon source, pH, temperature
and granular sludge (GS). Methane production was measured. Higher COD removal
and methane production were obtained at 3.5–7.5 g sorbitol/l, with an initial
pH of 9–9.5, and at 30–37 °C with 4.18–5.02 g/l of VSS. At these conditions VFA
and alcohols were consumed more and produced three times more methane than with
1.7 g/l VSS of granular sludge as inoculum. A strong relation between
methanogenic activity, COD removal efficiency was observed for all the initial
COD concentrations studied. The methanogenic stage was inhibited by the
presence intermediary products such as VFA in excess, which caused a drop in pH
and inhibited methanogenesis. This fact demonstrated the importance of
monitoring the production and consumption of VFA as a direct indicator for the
physiological condition of the reactor. The treatment of easily acidifying
wastewater like used in this case can be achieved with a detailed kinetic study
on the production and consumption of intermediary products to establish the
optimum parameters for higher efficiency of COD removal and methane production.
Copyright (C) Chemistry Dept., Moscow State University, 2002
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