Microbial growth reduction in sewage sludge by stirred ball mill disintegration and estimation by respirometry

BACKGROUND: Excess biomass generation in wastewater treatment plants is an unavoidable byproduct of the degradation process. Treatment and disposal of sewage sludge from wastewater treatment plants accounts for about half or even up to 60% of the total operating cost. The present study focuses on the reduction of excess sludge generation by engineering the microbes through mechanical energy inputs by means of stirred ball milling. RESULTS: The significant achievement of this study is microbial growth reduction of up to 89% at an applied specific energy of 15301 kJ kg(-1). The degree of disintegration of microbial cells was substantiated by estimating the degree of inactivation (DDO), degree of soluble chemical oxygen demand (COD) release (DDCOD), particle size and microscopic examination. The effect of disintegration on sludge microbial growth reduction is proved by respirometric studies. CONCLUSIONS: Sludge disintegration employing stirred ball milling is proved to be a worthwhile pretreatment process for reducing the sludge microbial growth in activated sludge treatment processes. (C) 2007 Society of Chemical Industry.