餐厨垃圾是生活垃圾分类收运处理的重要对象，具有高含水率、高有机质含量等特点。厌氧消化是餐厨垃圾处理的常用手段，兼具资源回收和降解污染物的特点，包括单相厌氧消化（SPAD）和两相厌氧消化（TPAD）两种类型，一般认为后者更为稳定，但对其相对于SPAD是否具有处理效率的优势还存在不同意见。围绕这一问题，本研究通过一系列长期运行实验，系统分析了TPAD在不同运行条件下的性能，重点归纳了pH、有机负荷（OLR）和固体停留时间（SRT）等对产酸相发酵特性以及产甲烷规律的影响。研究主要结论如下： （1）pH条件会影响餐厨垃圾厌氧发酵时的发酵类型。当pH在3.2~4.5范围内，发酵类型均为乳酸发酵，产物主要包括乳酸、乙醇、乙酸；其中，在pH3.2~4.2时，Lactobacillus相对丰度在90%以上，且以同型乳酸发酵为主；在pH4.5时，除Lactobacillus外，Bifidobacterium丰度增加至25.4%，异型乳酸发酵增强；pH为4.7~5.0时，发酵类型为丁酸发酵，Megasphaera和一些产氢菌丰度增加；当pH为6.0时，发酵类型呈现为混酸发酵，Prevotella和Megasphaera为优势菌，相对丰度分别为57.5%和27.5%。 （2）餐厨垃圾在pH4.5和6.0条件发酵时，水解率最高，分别为50.3%和47.8%；而不加碱时，pH会随产酸过程自动降至4.0以下，系统呈现乳酸发酵，水解率最低，仅30.1%。不同发酵类型会轻微影响产甲烷潜力，产酸相pH为4.5和6.0时，发酵产物的产甲烷潜力最大。与餐厨垃圾SPAD相比，TPAD系统的优势在于消化周期明显缩短。 （3）SPAD的有机负荷率（OLR）应控制在3.2 g/(L·d)以下，更高负荷会导致系统酸化。基于混酸发酵（pH6.0）或异型乳酸发酵（pH4.5）的TPAD在低OLR下可显著提升甲烷产率21~27%，但当OLR高于2.4 g/(L·d)时，产酸相pH调节加碱引起产甲烷相Na+的积累，抑制产甲烷过程，其适宜的产酸相和产甲烷相SRT组合为8+42天。不控制pH的TPAD系统在低OLR条件下，甲烷产率和甲烷含量与SPAD系统没有显著差异，但该系统却能在OLR达到3.7 g/(L·d)时仍保持稳定运行，此时最佳SRT组合为4+22天，有机质降解率可达到82.7%，甲烷产量达到397 ml/g VS。

Food waste is an important object of municipal solid waste classification, collection, transportation and treatment. Anaerobic digestion is a common method of food waste treatment, which has the characteristics of resource recovery and pollutant degradation, including single-phase anaerobic digestion (SPAD) and two-phase anaerobic digestion (TPAD). Generally, TPAD is considered to be more stable, but there are different opinions on whether it can show higher treatment efficiency than SPAD. To solve this problem, this study systematically analyzed the performance of TPAD under different operating conditions through a series of long-term running experiments, and focused on 、、the effects of pH, organic load rate(OLR) and solids retention time (SRT) to characteristics of acid-producing and methane-producing. The main conclusions are as follows: (1) The pH condition affected the type of fermentation in the anaerobic fermentation of food waste. When the pH was in the range of 3.2–4.5, the fermentation types were all lactic acid fermentation. The products mainly included lactic acid, ethanol and acetic acid. The relative abundance of Lactobacillus is above 90% at pH 3.2–4.2, and homolactic acid fermentation was dominant. At pH 4.5, the abundance of Bifidobacterium increased to 25.4%, which increased the proportion of heterolactic acid fermentation. When the pH was 4.7–5.0, the fermentation type was butyric acid fermentation, and the abundance of Megasphaera and other hydrogen-producing bacteria increased. When the pH was 6.0, the fermentation type was mixed-acid fermentation, Prevotella and Megasphaera were dominant bacteria, and the relative abundance were 57.5% and 27.5%, respectively. (2) During the fermentation process, the hydrolysis rate was the highest at pH 4.5 and 6.0, reaching 50.3% and 47.8%, respectively. Without pH control, the pH would automatically drop to below 4.0 with the production of acid. The system showed lactic acid fermentation and hydrolysis rate was the lowest (30.1%). Different fermentation types slightly affected the methanol potential. When the pH of the acidogenesis phase were 4.5, the biochemical methane potential of the fermentation product was the largest. Compared with SPAD, the advantage of the TPAD system was that the period of digestion was significantly shortened. (3) The organic load rate (OLR) of SPAD should be controlled below 3.2 g/(L·d), and higher OLR would lead to system acidification. TPAD based on mixed acid fermentation (pH6.0) or heterolactic fermentation (pH4.5) could significantly increased methane production by 21-27% at low OLR. However, when OLR was higher than 2.4 g/(L·d), the accumulation of Na+ in methanogenic phase inhibited methanogenic process due to alkali addition of acidogenesis phase. The appropriate SRT distributions (acid phase and methanogenic phase) was 8+42 days. Under low OLR condition, the TPAD system without pH control had no significant difference in methane yield and methane content with SPAD system, but the system could maintain stable operation when OLR reached 3.7 g/(L·d). At this time, the optimal SRT distributions was 4+22 days, the degradation rate of organic matter reached 82.7%, and the methane production reached 397 ml/g VS.