Volatile fatty acids (VFAs) are intermediates of anaerobic digestion with high value and wide range of usage. Co-digestion of sewage sludge and external organic waste (OW) for VFA production can help achieve both resource recovery and ensure sustainable and innovative waste management. In view of this, the effect of substrate proportions on VFA production from co-digestion of primary sewage sludge and OW is studied. Long-term operation in a semi-continuous reactor was performed to assess the resilience of such a system and the VFA-rich effluent was tested for its ability to be used as carbon source for denitrification. Co-digestion was initially carried out in batch reactors with OW proportion of 0%, 25%, 50%, 75%, 100% in terms of COD and scaled up in a semi-continuous reactor operation with 50% OW. In the short-term operation in the batch mode, acetic acid dominated, however, increasing OW fraction resulted in increased valeric and caproic acid production. Moreover, in the long-term semi-continuous operation, caproic acid dominated, accounting for ≈55% of VFAs. The VFA-rich effluent from the semi-continuous reactor achieved the highest denitrification rate as a carbon source when compared with acetic acid and methanol. The results demonstrate that co-fermentation can increase VFA yield and shift products from acetic acid to caproic acid in long-term operation and the VFAs can be used within wastewater treatment plants to close the loop.

挥发性脂肪酸（VFA）是厌氧消化的中间体，具有很高的价值和广泛的用途。用于VFA生产的污水污泥和外部有机废物（OW）的共消化可以帮助实现资源回收并确保可持续和创新的废物管理。有鉴于此，研究了底物配比对一次消化污泥和OW共同消化对VFA生产的影响。在半连续反应器中进行了长期操作以评估该系统的弹性，并测试了富含VFA的流出物用作脱氮碳源的能力。共消化最初是在间歇式反应器中进行的，以COD计，OW比例为0％，25％，50％，75％，100％，然后在OW为50％的半连续反应器操作中进行放大。在批处理模式下的短期操作中，乙酸占主导地位，但是，OW分数的增加导致戊酸和己酸产量的增加。此外，在长期半连续操作中，己酸占主导地位，约占VFA的55％。与乙酸和甲醇相比，半连续反应器中富含VFA的出水作为碳源实现了最高的反硝化率。结果表明，共发酵可提高VFA产量，并在长期运行中将产物从乙酸转变为己酸，并且VFA可用于废水处理厂以封闭环路。与乙酸和甲醇相比，半连续反应器中富含VFA的出水作为碳源实现了最高的反硝化率。结果表明，在长期运行中，共发酵可以提高VFA的收率并使产物从乙酸转变为己酸，并且VFA可以在废水处理厂内使用，以闭合回路。与乙酸和甲醇相比，半连续反应器中富含VFA的出水作为碳源实现了最高的脱氮率。结果表明，共发酵可提高VFA产量，并在长期运行中将产物从乙酸转变为己酸，并且VFA可用于废水处理厂以封闭环路。