Abstract:

Biological drying was employed to treat the dewatered sludge derived from sewage treatment plants, the effects of residence time and air volume on the bio drying process were investigated under continuous operating conditions, and the mechanism of water removal was elucidated. After 8d, the results showed that, the average reactor temperature in the system with residence time of 4d was 61.2℃, and the average biodrying index was 6.1. When the intensity of induced air was 0.95m³/(h·kg VS), the reactor temperature usually fluctuated within the range of 51.9—64.6℃, and the water removal and the apparent water reduction were 35.55% and 22.90kg, respectively. When the air flowrate increased to 1.30m³/(h·kg VS), the moisture reduction slightly improved but it was not significant. In a sludge biodrying system, those normal and mesophilic microorganisms decayed, then Firmicutes became the dominant microbial phylum, and the abundance of Bacillus in the sludge compost was above 75%; the fluorescence intensity of microorganisms in the central area of the reactor increased to 837.5, but the proportion of live bacteria was only 14.6%. After the wet mixture was added to the reactor, the dissolved organic matters in the feeding presented a rapid increase due to the fact that the sludge experienced thermophilic digestion, the contents of soluble protein and polysaccharide increased to 5.6mg/g and 5.0mg/g, respectively. The analysis of low field Nuclear Magnetic Resonance showed that the main form of water in wet sludge was bound water. With the biodrying process continued, the relaxation time of sludge samples became short, indicating the water migration slowed down, thus the moisture reduction was no longer obvious. Based on the analysis of water and heat balance, the releasing biological heat was 1.91MJ/d for the biodrying system with 4d residence time and 0.95m³/(h·kg VS) aeration intensity, and the efficiency of heat utilization was 65.58%. The moisture reduction was directly related to the temperature and the aeration intensity in the bio drying system, and it was also affected by the factors such as the content of organic matters and the relative humidity of water vapor.

Key words: municipal sewage sludge, bio-drying, exiting form of moisture, water and heat balance, vapor pressure

摘要：

采用生物干化技术处理污水厂脱水污泥，在连续运行条件下考察物料停留时间和引风量对污泥生物干化进程的影响，探究水分去除作用机制。连续运行8天后结果表明，物料停留时间为4天的生物干化体系平均堆温为61.2℃，生物干化指数均值为6.1。引风强度为0.95m³/(h·kg VS)时，堆体温度通常维持在51.9~64.6℃，水分去除率与表观减水量分别为35.55%、22.90kg；风量增大至1.30m³/(h·kg VS)时，除水效果略有提升但并不明显。污泥生物干化体系中，常温/中温微生物快速衰亡并溶胞，Firmicutes成为优势微生物门类，具有芽孢的微生物种属Bacillus在堆体中的丰度均不低于75%；堆体中心区微生物荧光强度上升至837.5，但活菌占比仅为14.6%。湿污泥投加后，随着堆体温度快速上升，进料区溶解性有机质含量明显提高，可溶性蛋白和多糖含量分别上升至5.6mg/g、5.0mg/g。低场核磁共振测试结果显示，湿污泥中水分赋存形态主要为结合水。随着生物干化进程的推进，污泥样本弛豫时间缩短，水分迁移率降低，物料中水分去除速率减慢。基于水热平衡分析，物料停留时间4d、引风量0.95m³/(h·kg VS)的污泥干化体系生物产热高达1.91MJ/d，热量利用效率达到65.58%；水分去除与堆体温度、引风量直接相关，也受到污泥中有机质含量、水汽相对湿度等因素影响。

关键词: 污水厂污泥, 生物干化, 水分赋存形态, 水热平衡, 蒸气压