Department of Urban Water Management, Technical University of Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany; Berlin Centre of Competence for Water, Cicerostrasse 24, 10709 Berlin, Germany.
Department of Urban Water Management, Technical University of Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.
Water Res. 2021 Sep 1;202:117465. doi: 10.1016/j.watres.2021.117465. Epub 2021 Jul 29.
Thermal alkaline pretreatment (TAP) of waste activated sludge (WAS) before anaerobic digestion (AD) was reviewed. Focus of the review was on impact of TAP process parameters on biomethane yield (BY) and kinetics of AD and downstream dewatering. With higher initial biodegradability of untreated WAS, effect of TAP on BY decreases. Depending on initial biodegradability, BY increase of 22-97% is expected. Treatment temperatures below 100 °C showed to be as effective as temperatures higher than 100 °C in terms of BY increase. Alkali dosage and resulting initial pH have a significant effect on BY increase and showed to have an optimum range of 40-60 mg NaOH per g total solids (TS) of sludge. It is advised that alkali is dosed based on solids content in WAS and monitored by pH. Treatment time of 1.5-5 h is sufficient for an effective low temperature TAP (T < 100 °C), with longer treatment times showing no positive impact on BY increase. Load of sludge liquor with organics and nutrients increases with more intensive TAP conditions. Despite kinetic enhancement of hydrolysis step in AD, more research is needed to clarify if TAP improves kinetics of entire AD process which determines required digester volume. Impact of TAP on dewaterability of digestate is ambiguous and needs more investigation using standardized methods, also with regards to potential effects on polymer demand. Findings of experimental studies were reflected against available data from commercialized TAP process of Pondus®, throughout review. Finally, important process design parameters of TAP such as input TS and point of alkali dosage are discussed and recommendations for future research are presented.
本文回顾了在厌氧消化（AD）之前对废活性污泥（WAS）进行热堿预处理（TAP）的情况。审查的重点是 TAP 工艺参数对生物甲烷产量（BY）和 AD 及下游脱水动力学的影响。由于未经处理的 WAS 初始可生物降解性较高，TAP 对 BY 的影响会降低。根据初始可生物降解性的不同，预计 BY 会增加 22-97%。在相同的 BY 增加效果下，处理温度低于 100°C 与高于 100°C 一样有效。碱剂量和由此产生的初始 pH 值对 BY 的增加有显著影响，且碱剂量和初始 pH 值存在 40-60mgNaOH/g 总固体（TS）污泥的最佳范围。建议根据 WAS 的固体含量投加碱，并通过 pH 值进行监测。对于有效的低温 TAP（T < 100°C），1.5-5 小时的处理时间就足够了，更长的处理时间对 BY 的增加没有积极影响。随着 TAP 条件的加强，污泥液中的有机物和养分的负荷会增加。尽管 AD 中水解步骤的动力学得到了增强，但仍需要进一步的研究来阐明 TAP 是否会改善决定所需消化罐体积的整个 AD 过程的动力学。TAP 对消化物脱水性能的影响尚不清楚，需要使用标准化方法进行更多研究，还需要考虑到对聚合物需求的潜在影响。本文在综述中反映了实验研究的结果，并与商业化的 Pondus®TAP 工艺的现有数据进行了对比。最后，讨论了 TAP 的重要工艺设计参数，如输入 TS 和碱投加点，并提出了未来研究的建议。
