A thermophilic/mesophilic dual digestion system for treating waste activated sludge

✍ Scribed by R Roberts; Son Le; C F Forster

• Publisher: Wiley (John Wiley & Sons)
• Year: 1999
• Tongue: English
• Weight: 105 KB
• Volume: 74
• Category: Article
• ISSN: 0268-2575
• DOI: 10.1002/(sici)1097-4660(199905)74:5<445::aid-jctb65>3.0.co;2-0

✦ Synopsis

Five con®gurations for a dual digestion were examined. The units were based on three 5 dm 3 completely stirred tank reactors (CSTR). A ®rst-stage thermophilic digester was used to provided the feed to each of the two second-stage mesophilic (35 °C) digesters. The thermophilic digester was operated initially at 55 °C with a hydraulic retention time of 4 h and then, later, at 60 °C with a hydraulic retention time of 3 h. The mesophilic digesters were operated at hydraulic retention times of 9, 12 and 15 days. In terms of volatile solids' (VS) reduction, the systems with a ®rst stage at 60 °C gave the better performance. However, based on the speci®c methane yield (m 3 CH 4 per kg VS removed), the con®guration with a ®rst stage operating at 55 °C and a secondary digester with a hydraulic retention time of 12 days was the most effective.