KINETIC ASSESSMENT OF VOLATILE FATTY ACIDS AS STRATEGY TO MAINTAIN THE SUSTAINABILITY OF THE BIODEGRADATION OF CHEMICAL OXYGEN DEMAND OF EASILY ACIDIFYING WASTEWATER

摘要

Kinetics of the production and consumption of volatile fatty acids (VFAs) such as acetic,propionic,butyric acids 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/1,with an initial pH of 9-9.5,and at 30-37°C with 4.18-5.02 g/1 of VSS.Under these conditions VFAs and alcohols were consumed more and produced three times more methane than with 1.7 g/1 VSS of granular sludge as inoculum.A strong relation between methanogenic activity and COD removal efficiency was observed for all the initial COD concentrations studied.The methanogenic stage was inhibited by the presence of intermediary products such as VFAs in excess,which caused a drop in pH and inhibited methanogenesis.This fact demonstrated the importance of monitoring the production and consumption of VFAs as a direct indicator for the physiological condition of the reactor.The treatment of easily acidifying wastewater such as used in this case can be achieved with a detailed kinetic study of the production and consumption of intermediary products to establish the optimum parameters for higher efficiency of COD removal and methane production.