Impacts of pre-sun-drying on sewage sludge compost

The aim of this study was to analyze the impacts of pre-sun-drying on sewage sludge compost. Comparative analysis was focused on the following parameters: moisture content (MC), pH value, total organic carbon (TOC), volatile solids (VS), water soluble total nitrogen (WSTN), ammonia nitrogen (AN), and dehydrogenase activity (DA). The results show that: the sun-drying process can quickly reduce initial moisture content from 82% to 77.7%. But the initial TOC and VS decreased from 356 g/kg and 59% to 326 g/kg and 50%, and the initial WSTN content was also decrease from 3.5 g/kg to 1.9 g/kg. As compost proceeded, the lower moisture content had slowed down the dehydrogenase activity (with an average of 271 μg TF/(g·h) vs. 199 μg TF/(g·h)). And pH value reached a maximum of 9.35 (non-drying) and 8.79 (air-drying) respectively, which had something to do with the more NH₃-N (12.2 g/kg vs. 4.4 g/kg) formed in the non-drying compost of the thermophilic phase.