Anaerobic digestion (AD) is the most commonly applied end-treatment for the excess of waste activated sludge (WAS) generated in biological wastewater treatment processes. The efficacy of different typologies of pre-treatments in liberating intra-cellular organic substances and make them more usable for AD was demonstrated in several studies. However, the production of new extracellular polymeric substances (EPSs) that occur during an AD process, due to microbial metabolism, self-protective reactions and cell lysis, partially neutralizes the benefit of pre-treatments. The efficacy of post- and inter-stage treatments is currently under consideration to overcome the problems due to this unavoidable byproduct.

This work compares three scenarios in which low-temperature (<100 °C) thermal and hybrid (thermal+alkali) lysis treatments were applied to one sample of WAS and two samples of digestate with hydraulic retention times (HRTs) of 7 and 15 days. Batch mesophilic digestibility tests demonstrated that intermediate treatments were effective in making the residual organic substance of a 7-day digestate usable for a second-stage AD process. In fact, under this scenario, the methane generated in a two-stage AD process, with an in-between intermediate treatment, was 23% and 16% higher than that generated in the scenario that considers traditional pre-treatments carried out with 4% NaOH at 70 and 90 °C respectively. Conversely, in no cases (70 or 90 °C) the combination of a 15-day AD process, followed by an intermediate treatment and a second-stage AD process, made possible to obtain specific methane productions (SMPs) higher than those obtained with pre-treatments.

The results of the digestibility tests were used for a tecno-economic assessment of pre- and intermediate lysis treatments in a full scale wastewater treatment plant (WWTP, 2,000,000 p.e.). It was demonstrated that the introduction of thermal or hybrid pre-treatments could increase the revenues from the electricity sale by between 13% and 25%, in comparison with the present scenario (no lysis treatments). Conversely, intermediate treatments on a 7-day digestate could provide a gain of 26% or 32%, depending on the process temperature (70 or 90 °C).

厌氧消化（AD）是生物废水处理过程中产生的多余的活性污泥（WAS）过量使用的最普遍的最终处理方法。在几项研究中证明了不同类型的预处理在释放细胞内有机物质并使它们更适用于AD方面的功效。但是，由于微生物的代谢，自我保护反应和细胞裂解，AD过程中产生的新的细胞外聚合物质（EPS）的产生部分抵消了预处理的益处。当前正在考虑阶段后和阶段间治疗的功效，以克服由于这种不可避免的副产物而引起的问题。

这项工作比较了三种情况，其中将低温（<100°C）热裂解和混合（热+碱）裂解处理应用于一个WAS样品和两个消化液样品，其水力停留时间（HRT）为7天和15天。分批中温消化率测试表明，中间处理有效地使7天消化液中的残留有机物可用于第二阶段的AD处理。实际上，在这种情况下，经过中间处理的中间阶段，在两阶段AD工艺中产生的甲烷比考虑到传统预处理以4％进行的情况下产生的甲烷分别高23％和16％。分别在70和90°C下的NaOH。相反，在任何情况下（70或90°C），都不会进行15天的广告宣传活动，

消化率测试的结果用于全面污水处理厂（WWTP，2,000,000 pe）中裂解前和中间裂解处理的技术经济评估。事实证明，与目前的方案（无裂解处理）相比，采用热预处理或混合预处理可以使电力销售收入增加13％至25％。相反，根据过程温度（70或90°C），对7天消化液进行的中间处理可增加26％或32％。