Watts S, Hamilton G, Keller J
Advanced Wastewater Management Centre, University of Queensland, Australia.
Water Sci Technol. 2006;53(8):149-57. doi: 10.2166/wst.2006.245.
A two-stage thermophilic-mesophilic anaerobic digestion pilot-plant was operated solely on waste activated sludge (WAS) from a biological nutrient removal (BNR) plant. The first-stage thermophilic reactor (HRT 2 days) was operated at 47, 54 and 60 degrees C. The second-stage mesophilic digester (HRT 15 days) was held at a constant temperature of 36-37 degrees C. For comparison with a single-stage mesophilic process, the mesophilic digester was also operated separately with an HRT of 17 days and temperature of 36-37 degrees C. The results showed a truly thermophilic stage (60 degrees C) was essential to achieve good WAS degradation. The lower thermophilic temperatures examined did not offer advantages over single-stage mesophilic treatment in terms of COD and VS removal. At a thermophilic temperature of 60 degrees C, the plant achieved 35% VS reduction, representing a 46% increase compared to the single-stage mesophilic digester. This is a significant level of degradation which could make such a process viable in situations where there is no primary sludge generated. The fate of the biologically stored phosphorus in this BNR sludge was also investigated. Over 80% of the incoming phosphorus remained bound up with the solids and was not released into solution during the WAS digestion. Therefore only a small fraction of phosphorus would be recycled to the main treatment plant with the dewatering stream.
一个两级嗜热-中温厌氧消化试验装置仅以生物脱氮（BNR）厂的剩余活性污泥（WAS）为原料运行。第一阶段的嗜热反应器（水力停留时间为2天）在47、54和60摄氏度下运行。第二阶段的中温消化器（水力停留时间为15天）保持在36 - 37摄氏度的恒定温度。为了与单级中温工艺进行比较，中温消化器也单独运行，水力停留时间为17天，温度为36 - 37摄氏度。结果表明，真正的嗜热阶段（60摄氏度）对于实现良好的WAS降解至关重要。在所研究的较低嗜热温度下，就化学需氧量（COD）和挥发性固体（VS）去除而言，并不比单级中温处理具有优势。在嗜热温度为60摄氏度时，该装置实现了35%的VS减少，与单级中温消化器相比增加了46%。这是一个显著的降解水平，这可能使这样的工艺在没有产生初沉污泥的情况下可行。还研究了该BNR污泥中生物储存的磷的去向。超过80%的进入的磷仍然与固体结合，在WAS消化过程中没有释放到溶液中。因此，只有一小部分磷会随着脱水水流回主处理厂。
