BIOHYDROGEN PRODUCTION FROM WASTE SLUDGE

Waste biological sludge from a wastewater treatment plant contains high levels of organic matter (for example, carbonhydrates and proteins) and thus are a potential substrate for producing hydrogen. Using sludge as the substrate for fermentative hydrogen production offers several advantages over the use of other biomass sources (plants, animals and their organic waste products). It is available at little or no cost. It is of great significance to produce hydrogen from sludge by fermentative hydrogen production, because it can not only treat sludge but also produce very clean energy. Due to low hydrogen yield (i.e., 1.21 mL H-2/g volatile solid (VS)), several methods of sludge pretreatment such as ultrasonication, acidification, basification, thermal pretreatment, freezing-and-thawing have been used to enhance the hydrogen yield. Pre-treatment can increase the efficiency of anaerobic hydrolyze step of sludge by releasing the insoluble organic matter to water. For example hydrogen yields were improved to 3.25 mL H-2/g VS with acidification, 1.46 mL H-2/g VS with basification, 8.62 mL H-2/g VS with thermal pretreatment and to 3.83 mL H-2/g VS with ultrasonication. Pre-treatments not only released insoluble organic matter into water to increase the efficiency of fermentation, but also inactivated methanogenic bacteria in the substrate to reduce their consumption of hydrogen.