The stability of an anaerobic bioreactor is a function of alkalinity that provides buffer capacity to maintain a suitable pH for anaerobic microorganisms. The greatest advantage of membrane distillation (MD) is the high rejection of most solutes, including alkaline salt, and it has a high potential to retain alkalinity for the anaerobic system. For the first time, a thermophilic anaerobic granular bioreactor integrated with an MD membrane to maintain the buffered pH was studied in an anaerobic bioreactor without alkalinity supplement. This study presented a comparison between a conventional thermophilic anaerobic bioreactor (TAn1) and a thermophilic anaerobic bioreactor integrated with a MD (TAn2-MD). The two TAns (TAn1 and TAn2) were operated in the same conditions except there was no alkalinity feeding for the TAn2-MD. The results showed that the pH in the TAn2-MD unit was always higher than 6.8 with the organic loading rates from 6 to 18 kg COD/m³/day. However, to maintain the pH of the TAn1 unit at the same level as the TAn2-MD unit, the minimum alkalinity requirements for TAn1 were 1.5, 1.56, 1.62, and 1.8 g/L as CaCO₃ at an organic loading rate of 6, 10, 14, and 18 kg COD/m³/day, respectively. Although there was no alkalinity supplement for the TAn2-MD system, two stability indexes, FOS/TAC (volatile organic acids to buffer capacity) and IA/PA (intermediate alkalinity to partial alkalinity), indicated the system was operated at a stable condition. In summary, the designed TAn2-MD can accomplish high-efficiency organic carbon removal (higher than 99.4%) without alkalinity supplement, achieve zero-liquid-discharge, and reclaim high-quality wastewater in one step.

厌氧生物反应器的稳定性是碱度的函数，碱度提供缓冲能力以维持适合厌氧微生物的pH。膜蒸馏（MD）的最大优势是对大多数溶质（包括碱性盐）的高排斥，并且对于厌氧系统具有很高的保留碱度的潜力。首次在不添加碱度的厌氧生物反应器中研究了与MD膜集成以维持缓冲pH值的嗜热厌氧颗粒生物反应器。这项研究提出了传统的嗜热厌氧生物反应器（TAn1）和集成了MD（TAn2-MD）的嗜热厌氧生物反应器之间的比较。两个TAn（TAn1和TAn2）在相同条件下运行，除了TAn2-MD没有碱度进料。³ /天。但是，为了将TAn1单元的pH维持在与TAn2-MD单元相同的水平，在有机负载率为6时，TAn1的最低碱度要求为CaCO _3的1.5、1.56、1.62和1.8 g / L。分别为10、14和18千克COD / m ³ /天。尽管没有为TAn2-MD系统添加碱度，但两个稳定性指标FOS / TAC（挥发性有机酸至缓冲容量）和IA / PA（中等碱度至部分碱度）表明系统在稳定条件下运行。综上所述，设计的TAn2-MD无需碱化即可实现高效有机碳去除（高于99.4％），实现零液体排放，并一步一步回收优质废水。