Compostability of lime-flocculated sewage sludge

Recent developments in wastewater treatment are resulting in the production of substantial amounts of chemically [Ca(OH)₂ and Al₂(SO₄)₃·H₂O] treated sludges in need of further treatment before disposal. Although a seemingly suitable method, an unfavorable pH and low volatile solids content constitute serious problems for composting. Hence, an investigation was made of the feasibility of window composting Ca(OH)₂ (lime) precipitated sludge (approximately 25% solids) when mixed with a bulking agent. Bulking agents tried were the paper fraction of municipal refuse and chipped tree and shrub trimmings. Both bulking agents were tried in their raw and in their composted states. Initial mixing was by way of a specially designed hammermill, and subsequent mixing was done manually. Compostability was measured by rate and extent of the temperature rise and fall and by destruction of volatile solids. According to the results, lime exerted no inhibitory influence on the composting process. However, the high ratio of biologically inert material to volatile solids resulted in a shortage of nutrients for the bacteria. Consequently, temperatures attained were neither sufficiently high nor of long enough duration to ensure the pathogen destruction required for public health safety.     

基于特征和知识的精密注塑模设计和制造系统

采用先进的CAD/CAM技术对传统模具设计制造方法进行改造,是提高模具设计制造质量和效率的关键.此文提出基于特征和知识的才法构造精密注塑模设计和制造系统,并介绍了系统的总体方案和系统包含的各模块功能.这一系统是浙江省科委八五攻关项目“精密注塑模设计和制造(CAD/CAM)技术”的核心.     

Preface

Preface

Preface