Dark fermentation of cheese whey (CW) for the production of biohydrogen generates an acidic effluent, containing high concentrations of volatile fatty acids, which needs to be further treated before disposal and possibly further valorised. This study develops a dual-chamber Microbial Electrolysis Cell (MEC) that achieves simultaneously the reduction of the organic content of this effluent to environmentally acceptable levels, along with bio-electrochemical reduction of CO to CH. The MEC was operated for 140 days and the effect of the following conditions on the MEC performance was examined: (a) the feed concentration of the acidic fermentate (in the range 6–81 g/L), (b) the conductivity of the feed modified via KCl addition (range 2–22 mS/cm), (c) the MEC operation mode (with or without catholyte renewal) and (d) the solids content (modified via CW filtration prior to its use). The results showed that high COD removal (>95 %) was achieved in all cases, along with a CH production of up to 1.1 mmol/g. The best performance of the cell was obtained for a feed COD concentration of ∼30 g/L and a feed conductivity of ∼15 mS/cm; these conditions resulted in a COD removal exceeding 99 %, a CH production of 1.1 mmol/g and a net energy production of 15.8 % compared to the energy demand of the system. The electrochemical study of the system revealed that higher and lower feed COD concentrations were characterized by higher internal resistances. The results indicate that the MEC can be exploited for further treatment and valorization of a high-strength effluent along with the production of CH with an energy surplus, as an efficient waste-to-energy technology.

中文翻译：

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双室微生物电解槽用于从奶酪乳清深色发酵废水中电合成甲烷


用于生产生物氢的奶酪乳清 (CW) 深色发酵会产生酸性废水，其中含有高浓度的挥发性脂肪酸，在处置前需要进一步处理，并可能进一步增值。本研究开发了一种双室微生物电解池 (MEC)，可同时将废水中的有机物含量降低至环境可接受的水平，同时通过生物电化学方式将 CO 还原为 CH。 MEC 运行了 140 天，并检查了以下条件对 MEC 性能的影响：(a) 酸性发酵液的进料浓度（范围为 6–81 g/L），(b) 发酵液的电导率通过添加 KCl（范围 2-22 mS/cm）修改进料，(c) MEC 操作模式（有或没有阴极电解液更新）和 (d) 固体含量（在使用前通过 CW 过滤修改）。结果表明，在所有情况下均实现了高 COD 去除率 (>95%)，同时 CH 产量高达 1.1 mmol/g。当进料 COD 浓度~30 g/L 和进料电导率~15 mS/cm 时，获得了电池的最佳性能；与系统的能源需求相比，这些条件导致 COD 去除率超过 99%，CH 产量为 1.1 mmol/g，净能源产量为 15.8%。系统的电化学研究表明，较高和较低的进料 COD 浓度的特点是较高的内阻。结果表明，MEC 可用于进一步处理高浓度废水并使其增值，同时生产具有能量剩余的 CH，作为一种高效的垃圾发电技术。