Effect of pH on Anaerobic Acidogenesis of Excess Sludge

Volatile fatty acids(VFAs) are recognized as the carbon sources suitable for enhanced biological phosphorus removal process.It is feasible to utilize the anaerobic fermentation of sludge to acquire biodegradable substrates for biological phosphorus removal in wastewater treatment plant.At the same time,the effect of sludge pollution on environment is reduced.The pH value is an important parameter to affect the anaerobic fermentation.The effect of different pH values on the anaerobic acidogenesis of excess sludge at 20 to 22 ℃ was investigated.The results show that VFAs production at pH 8 to 11 is higher than that at pH 4 to 7 in the fermentation period of 20 days.When the pH is controlled at 10,the maximal VFAs of 256.16 mgCOD/gVSS are achieved on the 12th day,which is almost 3 times of that at pH of 7.The VFAs are mainly composed of acetic acid,propionic acid,iso-butyric acid and iso-valeric acid.Besides,much soluble chemical oxygen demand(SCOD) is released under alkaline conditions.The released amounts of carbohydrates and protein under alkaline conditions are greater than those under acidic conditions,and the concentration of soluble protein is higher than that of carbohydrates.