State-of the-Practice for Dewatering of Thermally Hydrolyzed Digested Biosolids

摘要

Historically, centrifuges have outperformed belt filter presses (BFPs) in dewatering digested biosolids. However, results from several projects where wastewater solids have been treated by thermal hydrolysis process (THP) followed by mesophilic anaerobic digestion (MAD) have shown good results in BFP dewatering - with generally greater than 30 percent cake solids concentration. The authors propose that the main mechanism in THP is changing the structure of the exocellular polymeric substances (EPS) that binds water mainly to secondary solids and limits dewaterability and compressibility of the mixed solids. The digested biosolids after THP also has a much finer structure and this can lead to problems in capture rate and higher polymer dose with some centrifuges. This manuscript includes a summary of: 1) full-scale performance of the BFPs on thermal hydrolyzed digested biosolids at the 370 mgd DC Water Blue Plains Advanced Wastewater Treatment Plant (AWWTP), and 2) the evaluation and selection of final dewatering technology for thermally hydrolyzed biosolids at the Southeast Plant (SEP) operated by the San Francisco Public Utilities Commission (SFPUC). The manuscript also includes a detailed list of devices dewatering thermally hydrolyzed digested biosolids throughout the World. The information should help others in the evaluation and selection of the best dewatering technology for thermally hydrolyzed biosolids at other Wastewater Treatment Plants (WWTPs).