Understanding the performance of anaerobic digestion with thermal and biological pre-treatment at a pilot scale

Most of the organic matter during wastewater treatment is converted to a solid form known as sludge or biosolids. Because of the high price of sludge management and the strong demand for alternative energy sources, many studies have investigated the effect of various pretreatments during the anaerobic digestion of sludge for optimizing biogas production.The pretreatment methods alter the physical and chemical properties of sludge to make it more degradable by anaerobic digestion. The main goal of pretreatment is to disrupt the EPS matrix and cell wall and to make the available nutrients accessible to microbes thus speeding up the conversion of organic solids and methane productivity. In the last decade, the thermal hydrolysis process (THP) has been widely adopted as a pre-treatment technology in implementing advanced anaerobic digestion (AAD) to increase the energy recovery potential of the sludge. Of late, biological methods like heating, pasteurization, and hydrolysis (HpH) for removing toxic and other harmful substances are gaining traction as promising pretreatment technology, especially in the United Kingdom.THP comprises subjecting the feed sludge to high pressure and temperature, enhancing hydrolysis, while simultaneously overcoming the various constraints imposed by the high sludge bulk viscosity and limited suspended solids solubility. However, HpH is biological pre-treatments designed to separate acid-phase reactions from methanogenic reactions in the digester.This thesis aims to understand the performance of the thermal hydrolysis process and biological techniques pre treatment on the biodegradability of secondary, and digested sludge. The performance assessment was based on various characteristics of sludge before & after pre-treatment and after digestion to discern the effect of thermal and biological pre-treatments at the piolet-scale on General properties of sludge, macromolecules and, trace elements.