Department of Water Management, Delft University of Technology, Building 23 Stevinweg 1, 2628, Delft, The Netherlands.
Chemosphere. 2023 Aug;332:138896. doi: 10.1016/j.chemosphere.2023.138896. Epub 2023 May 9.
Full-scale thermal hydrolysis processes (THP) showed an increase in nutrients release and formation of melanoidins, which are considered to negatively impact methanogenesis during mesophilic anaerobic digestion (AD). In this research, fractionation of THP-sludge was performed to elucidate the distribution of nutrients and the formed melanoidins over the liquid and solid sludge matrix. Degradation of the different fractions in subsequent AD was assessed, and the results were compared with non-pre-treated waste activated sludge (WAS). Results showed that the THP-formed soluble melanoidins were partially biodegradable under AD, especially the fraction with molecular weight under 1.1 kDa, which was related to protein-like substances. The use of THP in WAS increased the non-biodegradable soluble chemical oxygen demand (sCOD) after AD, from 1.1% to 4.9% of the total COD. The total ammoniacal nitrogen (TAN) concentration only slightly increased during THP without AD. However, after AD, TAN released was 34% higher in the THP-treated WAS compared to non-treated WAS, i.e., 36.7 ± 0.7 compared to 27.4 ± 0.4 mgTANreleased/gCODsubstrate, respectively. Results from modified specific methanogenic activities (mSMAs) tests showed that the organics solubilised during THP, were not inhibitory for acetotrophic methanogens. However, after AD of THP-treated sludge and WAS, the mSMA showed that all analysed samples presented strong inhibition on methanogenesis due to the presence of TAN and associated free ammonia nitrogen (FAN). In specific methanogenic activities (SMAs) tests with incremental concentration of TAN/FAN and melanoidins, TAN/FAN induced strong inhibition on methanogens, halving the SMA at around 2.5 gTAN/L and 100 mgFAN/L. Conversely, melanoidins did not show inhibition on the methanogens. Our present results revealed that when applying THP-AD in full-scale, the increase in TAN/FAN remarkably had a greater impact on AD than the formation of melanoidins.
全规模热水解工艺 (THP) 显示出营养物质释放的增加和类黑素的形成，这被认为会对中温厌氧消化 (AD) 中的甲烷生成产生负面影响。在这项研究中，对 THP 污泥进行了分级，以阐明营养物质和形成的类黑素在液体和固体污泥基质中的分布。评估了随后在 AD 中不同级分的降解情况，并将结果与未经预处理的废活性污泥 (WAS) 进行了比较。结果表明，THP 形成的可溶性类黑素在 AD 下部分可生物降解，特别是分子量低于 1.1 kDa 的级分，这与蛋白质样物质有关。在 WAS 中使用 THP 会增加 AD 后不可生物降解的可溶性化学需氧量 (sCOD)，从总 COD 的 1.1%增加到 4.9%。THP 未经 AD 时，总氨氮 (TAN) 浓度仅略有增加。然而，AD 后，THP 处理的 WAS 中释放的 TAN 比未经处理的 WAS 高 34%，即 36.7 ± 0.7 与 27.4 ± 0.4 mgTANreleased/gCODsubstrate 相比。经过改良的特定产甲烷活性 (mSMAs) 测试的结果表明，THP 过程中溶解的有机物对乙酸营养型产甲烷菌没有抑制作用。然而，在 THP 处理的污泥和 WAS 的 AD 后，mSMA 表明，由于存在 TAN 和相关的游离氨氮 (FAN)，所有分析的样品对甲烷生成均表现出强烈的抑制作用。在 TAN/FAN 和类黑素的递增浓度的特定产甲烷活性 (SMAs) 测试中，TAN/FAN 对产甲烷菌产生强烈抑制，使 SMA 在约 2.5 gTAN/L 和 100 mgFAN/L 时减半。相反，类黑素对产甲烷菌没有抑制作用。我们目前的结果表明，在全规模应用 THP-AD 时，TAN/FAN 的增加对 AD 的影响明显大于类黑素的形成。
