Microbial communities of anaerobic digesters fed with palm oil mill effluent with the supplements of surfactant and iron

This study investigated the effects of various surfactants on soluble COD fraction and biogas production from palm oil mill effluent (POME). Cationic surfactant (CTAB) and nonionic surfactant (Tween 80; TW80) were found to adsorb onto POME's particulate matter, markedly reducing the soluble COD, unlike the anionic surfactant (SDS). The mechanism behind this phenomenon might be the adsolubilization of oil on particulate matter induced by the adsorbed surfactants. In terms of biogas production, SDS and CTAB at 0.1%w/v dramatically reduced the biogas yield, while applying TW80 .1%w/v did not show this negative effect. A synergistic effect was observed when combining TW80 (0.1%w/v) with iron(II) sulphate (400 mg/L), resulting in a 17% higher biogas yield compared to treatments using TW80 or FeSO4 alone. Moreover, the combination of TW80 and iron(II) sulphate increased the biogas production rate. Surprisingly, the water-soluble iron fraction remained consistent across all treatments, suggesting that the adsorption of TW80 on particulate matter may limit micelle formation. Importantly, the methane proportion in the generated biogas remained stable in all treatments. Microbial community analysis revealed that the introduction of TW80 and iron(II) sulphate had no discernible impact on the system's microbial community. The pretreatment with TW80 and iron supplement significantly enhanced biogas production and reduced the retention time of the anaerobic digestion system, all while maintaining biogas quality and microbial community stability.

本研究探究了多种表面活性剂（surfactant）对棕榈油厂废水（palm oil mill effluent, POME）溶解性化学需氧量组分及沼气（biogas）产量的影响。研究发现，阳离子表面活性剂（CTAB）与非离子表面活性剂吐温80（Tween 80; TW80）可吸附于POME的颗粒物上，显著降低溶解性化学需氧量，而阴离子表面活性剂（SDS）则无此类效果。该现象的潜在机制可能为吸附于颗粒物的表面活性剂诱导了油类在颗粒物表面的吸附增溶。在沼气产率方面，浓度为0.1%w/v的SDS与CTAB会大幅降低沼气产率，而相同浓度的TW80则未表现出该负面影响。当将0.1%w/v的TW80与400 mg/L硫酸亚铁（iron(II) sulphate）复配使用时，可观察到协同效应，其沼气产率较单独使用TW80或硫酸亚铁（FeSO4）提升17%。此外，该复配体系还提高了沼气生产速率。令人意外的是，所有处理组的水溶性铁组分均保持稳定，这表明TW80在颗粒物上的吸附可能限制了胶束的形成。值得注意的是，所有处理组生成的沼气中甲烷占比均未发生明显变化。微生物群落分析显示，添加TW80与硫酸亚铁对系统的微生物群落无显著影响。采用TW80与铁源预处理可显著提升沼气产量，缩短厌氧消化系统（anaerobic digestion system）的停留时间，同时维持沼气品质与微生物群落稳定性。