Muñoz Sierra Julian D, García Rea Víctor S, Cerqueda-García Daniel, Spanjers Henri, van Lier Jules B
Section Sanitary Engineering, Department of Water Management, Delft University of Technology, Delft, Netherlands.
KWR Water Research Institute, Nieuwegein, Netherlands.
Front Bioeng Biotechnol. 2020 Sep 30;8:565311. doi: 10.3389/fbioe.2020.565311. eCollection 2020.
Closing water loops in chemical industries result in hot and highly saline residual streams, often characterized by high strength and the presence of refractory or toxic compounds. These streams are attractive for anaerobic technologies, provided the chemical compounds are biodegradable. However, under such harsh conditions, effective biomass immobilization is difficult, limiting the use of the commonly applied sludge bed reactors. In this study, we assessed the long-term phenol conversion capacity of a lab-scale anaerobic membrane bioreactor (AnMBR) operated at 55°C, and high salinity (18 gNaL). Over 388 days, bioreactor performance and microbial community dynamics were monitored using specific methanogenic activity (SMA) assays, phenol conversion rate assays, volatile fatty acids permeate characterization and Illumina MiSeq analysis of 16S rRNA gene sequences. Phenol accumulation to concentrations exceeding 600 mgPhL in the reactor significantly reduced methanogenesis at different phases of operation, while applying a phenol volumetric loading rate of 0.12 gPhLd. Stable AnMBR reactor performance could be attained by applying a sludge phenol loading rate of about 20 mgPhgVSSd. maximum phenol conversion rates of 21.3 mgPhgVSS d were achieved, whereas conversion rates of 32.8 mgPhgVSS d were assessed in batch tests at the end of the operation. The absence of caproate as intermediate inferred that the phenol conversion pathway likely occurred via carboxylation to benzoate. Strikingly, the hydrogenotrophic SMA of 0.34 gCOD-CH gVSS d of the AnMBR biomass significantly exceeded the acetotrophic SMA, which only reached 0.15 gCOD-CH gVSS d. Our results indicated that during the course of the experiment, acetate conversion gradually changed from acetoclastic methanogenesis to acetate oxidation coupled to hydrogenotrophic methanogenesis. Correspondingly, hydrogenotrophic methanogens of the class Methanomicrobia, together with Synergistia, Thermotogae, and Clostridia classes, dominated the microbial community and were enriched during the three phases of operation, while the aceticlastic Methanosaeta species remarkably decreased. Our findings clearly showed that highly saline phenolic wastewaters could be satisfactorily treated in a thermophilic AnMBR and that the specific phenol conversion capacity was limiting the treatment process. The possibility of efficient chemical wastewater treatment under the challenging studied conditions would represent a major breakthrough for the widespread application of AnMBR technology.
化工行业中封闭水回路会产生高温且高盐的残余物流，其特点通常是强度高，且含有难降解或有毒化合物。如果这些化合物可生物降解，那么这些物流对厌氧技术具有吸引力。然而，在如此恶劣的条件下，有效的生物质固定化很困难，这限制了常用的污泥床反应器的使用。在本研究中，我们评估了在55°C和高盐度（18 gNa/L）条件下运行的实验室规模厌氧膜生物反应器（AnMBR）的长期苯酚转化能力。在388天的时间里，使用特定产甲烷活性（SMA）测定、苯酚转化率测定、挥发性脂肪酸渗透物表征以及16S rRNA基因序列的Illumina MiSeq分析来监测生物反应器性能和微生物群落动态。当苯酚体积负荷率为0.12 gPh/L·d时，反应器中苯酚积累至浓度超过600 mgPh/L会在不同运行阶段显著降低产甲烷作用。通过应用约20 mgPh/gVSS·d的污泥苯酚负荷率，可以实现AnMBR反应器性能的稳定。实现了21.3 mgPh/gVSS·d的最大苯酚转化率，而在运行结束时的批次试验中评估的转化率为32.8 mgPh/gVSS·d。己酸盐作为中间产物的缺失表明苯酚转化途径可能是通过羧化作用生成苯甲酸盐。引人注目的是，AnMBR生物质的氢营养型SMA为0.34 gCOD-CH/gVSS·d，显著超过了仅达到0.15 gCOD-CH/gVSS·d的乙酸营养型SMA。我们的结果表明，在实验过程中，乙酸转化逐渐从乙酸裂解产甲烷作用转变为与氢营养型产甲烷作用耦合的乙酸氧化。相应地，甲烷微菌纲的氢营养型产甲烷菌，连同协同菌纲、栖热袍菌纲和梭菌纲，在微生物群落中占主导地位，并在三个运行阶段中得到富集，而乙酸裂解型的甲烷八叠球菌属物种显著减少。我们的研究结果清楚地表明，高盐度含酚废水可以在嗜热AnMBR中得到满意的处理，并且特定的苯酚转化能力限制了处理过程。在具有挑战性的研究条件下实现高效化学废水处理的可能性将代表AnMBR技术广泛应用的一个重大突破。
