Cerruti Marta, Stevens Berber, Ebrahimi Sirous, Alloul Abbas, Vlaeminck Siegfried E, Weissbrodt David G
Department of Biotechnology, Delft University of Technology, Delft, Netherlands.
Department of Chemical Engineering, Sahand University of Technology, Tabriz, Iran.
Front Bioeng Biotechnol. 2020 Dec 17;8:557234. doi: 10.3389/fbioe.2020.557234. eCollection 2020.
Mixed-culture biotechnologies are widely used to capture nutrients from wastewater. Purple non-sulfur bacteria (PNSB), a guild of anoxygenic photomixotrophic organisms, rise interest for their ability to directly assimilate nutrients in the biomass. One challenge targets the aggregation and accumulation of PNSB biomass to separate it from the treated water. Our aim was to enrich and produce a concentrated, fast-settling PNSB biomass with high nutrient removal capacity in a 1.5-L, stirred-tank, anaerobic sequencing-batch photobioreactor (SBR). PNSB were rapidly enriched after inoculation with activated sludge at 0.1 gVSS L in a first batch of 24 h under continuous irradiance of infrared (IR) light (>700 nm) at 375 W m, with reaching 54% of amplicon sequencing read counts. SBR operations with decreasing hydraulic retention times (48 to 16 h, i.e., 1-3 cycles d) and increasing volumetric organic loading rates (0.2-1.3 kg COD d m) stimulated biomass aggregation, settling, and accumulation in the system, reaching as high as 3.8 g VSS L. The sludge retention time (SRT) increased freely from 2.5 to 11 days. Acetate, ammonium, and orthophosphate were removed up to 96% at a rate of 1.1 kg COD d m, 77% at 113 g N d m, and 73% at 15 g P d m, respectively, with COD:N:P assimilation ratio of 100:6.7:0.9 m/m/m. SBR regime shifts sequentially selected for (90%) under shorter SRT and non-limiting concentration of acetate during reaction phases, for (70%) under longer SRT and acetate limitation during reaction, and (10%) under higher biomass concentrations, underlying competition for substrate and photons in the PNSB guild. With SBR operations we produced a fast-settling biomass, highly (>90%) enriched in PNSB. A high nutrient removal was achieved by biomass assimilation, reaching the European nutrient discharge limits. We opened further insights on the microbial ecology of PNSB-based processes for water resource recovery.
混合培养生物技术被广泛用于从废水中捕获营养物质。紫色非硫细菌（PNSB）是一类厌氧光合混合营养生物，因其能够直接在生物质中同化营养物质而受到关注。一个挑战是针对PNSB生物质的聚集和积累，以便将其与处理后的水分离。我们的目标是在一个1.5升的搅拌罐式厌氧序批式光生物反应器（SBR）中富集并产生一种具有高营养去除能力的浓缩、快速沉降的PNSB生物质。在375 W/m²的红外（IR）光（>700 nm）连续照射下，以0.1 gVSS/L的活性污泥接种后，PNSB在第一批24小时内迅速富集，其在扩增子测序读数中占比达到54%。通过降低水力停留时间（从48小时降至16小时，即每天1 - 3个周期）和提高体积有机负荷率（从0.2 - 1.3 kg COD/d·m³）的SBR操作，刺激了系统中生物质的聚集、沉降和积累，最高达到3.8 g VSS/L。污泥停留时间（SRT）从2.5天自由增加到11天。乙酸盐、铵和正磷酸盐的去除率分别高达96%（去除速率为1.1 kg COD/d·m³）、77%（113 g N/d·m³）和73%（15 g P/d·m³），COD:N:P同化比为100:6.7:0.9 m/m/m。SBR模式转变依次选择了在较短SRT和反应阶段乙酸盐浓度非限制条件下的（90%）、在较长SRT和反应阶段乙酸盐限制条件下的（70%）以及在较高生物质浓度下的（10%），这表明PNSB群体中存在对底物和光子的竞争。通过SBR操作，我们产生了一种快速沉降的生物质，其中PNSB高度富集（>90%）。通过生物质同化实现了高营养去除，达到了欧洲营养物排放限值。我们为基于PNSB的水资源回收过程的微生物生态学提供了进一步的见解。
