Lenz Markus, Enright Anne Marie, O'Flaherty Vincent, van Aelst Adriaan C, Lens Piet N L
Sub-Department of Environmental Technology, Wageningen University, Bomenweg 2, 6700 EV, Wageningen, The Netherlands.
Appl Microbiol Biotechnol. 2009 May;83(2):377-88. doi: 10.1007/s00253-009-1915-x. Epub 2009 Mar 21.
Whole-cell immobilization of selenate-respiring Sulfurospirillum barnesii in polyacrylamide gels was investigated to allow the treatment of selenate contaminated (790 microg Se x L(-1)) synthetic wastewater with a high molar excess of nitrate (1,500 times) and sulfate (200 times). Gel-immobilized S. barnesii cells were used to inoculate a mesophilic (30 degrees C) bioreactor fed with lactate as electron donor at an organic loading rate of 5 g chemical oxygen demand (COD) x L(-1) day(-1). Selenate was reduced efficiently (>97%) in the nitrate and sulfate fed bioreactor, and a minimal effluent concentration of 39 microg Se x L(-1) was obtained. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis revealed spherical bioprecipitates of <or=2 microm diameter mostly on the gel surface, consisting of selenium with a minor contribution of sulfur. To validate the bioaugmentation success under microbial competition, gel cubes with immobilized S. barnesii cells were added to an Upflow Anaerobic Sludge Bed (UASB) reactor, resulting in earlier selenate (24 hydraulic retention times (HRTs)) and sulfate (44 HRTs) removal and higher nitrate/nitrite removal efficiencies compared to a non-bioaugmented control reactor. S. barnesii was efficiently immobilized inside the UASB bioreactors as the selenate-reducing activity was maintained during long-term operation (58 days), and molecular analysis showed that S. barnesii was present in both the sludge bed and the effluent. This demonstrates that gel immobilization of specialized bacterial strains can supersede wash-out and out-competition of newly introduced strains in continuous bioaugmented systems. Eventually, proliferation of a selenium-respiring specialist occurred in the non-bioaugmented control reactor, resulting in simultaneous nitrate and selenate removal during a later phase of operation.
研究了将呼吸亚硒酸盐的巴恩斯硫螺旋菌全细胞固定在聚丙烯酰胺凝胶中，以处理含有高摩尔过量硝酸盐（1500倍）和硫酸盐（200倍）的亚硒酸盐污染（790微克硒·升⁻¹）合成废水。用凝胶固定化的巴恩斯硫螺旋菌细胞接种中温（30℃）生物反应器，以乳酸作为电子供体，有机负荷率为5克化学需氧量（COD）·升⁻¹·天⁻¹。在添加硝酸盐和硫酸盐的生物反应器中，亚硒酸盐被有效还原（>97%），获得的最低出水浓度为39微克硒·升⁻¹。扫描电子显微镜结合能量色散X射线（SEM-EDX）分析显示，直径≤2微米的球形生物沉淀物大多位于凝胶表面，主要由硒组成，硫的含量较少。为了验证在微生物竞争下生物强化的成功，将含有固定化巴恩斯硫螺旋菌细胞的凝胶块添加到上流式厌氧污泥床（UASB）反应器中，与未进行生物强化的对照反应器相比，亚硒酸盐（24个水力停留时间（HRT））和硫酸盐（44个HRT）的去除时间更早，硝酸盐/亚硝酸盐去除效率更高。巴恩斯硫螺旋菌有效地固定在UASB生物反应器内，因为在长期运行（58天）期间亚硒酸盐还原活性得以维持，分子分析表明巴恩斯硫螺旋菌存在于污泥床和出水中。这表明特定细菌菌株的凝胶固定化可以取代连续生物强化系统中新引入菌株的洗出和竞争淘汰。最终，在未进行生物强化的对照反应器中出现了呼吸硒的专性菌增殖，导致在运行后期同时去除硝酸盐和亚硒酸盐。
