King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Division of Biological and Environmental Science and Engineering (BESE), Thuwal, 23955-6900, Saudi Arabia.
King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Division of Biological and Environmental Science and Engineering (BESE), Thuwal, 23955-6900, Saudi Arabia.
Water Res. 2020 Sep 15;183:116051. doi: 10.1016/j.watres.2020.116051. Epub 2020 Jun 16.
Nutrient limitation is a biofouling control strategy in reverse osmosis (RO) membrane systems. In seawater, the assimilable organic carbon content available for bacterial growth ranges from about 50 to 400 μg C·L, while the phosphorus concentration ranges from 3 to 11 μg P·L. Several studies monitored biofouling development, limiting either carbon or phosphorus. The effect of carbon to phosphorus ratio and the restriction of both nutrients on membrane system performance have not yet been investigated. This study examines the impact of reduced phosphorus concentration (from 25 μg P·L and 3 μg P·L, to a low concentration of ≤0.3 μg P·L), combined with two different carbon concentrations (250 C L and 30 μg C·L), on biofilm development in an RO system. Feed channel pressure drop was measured to determine the effect of the developed biofilm on system performance. The morphology of the accumulated biomass for both carbon concentrations was characterized by optical coherence tomography (OCT) and the biomass amount and composition was quantified by measuring total organic carbon (TOC), adenosine triphosphate (ATP), total cell counts (TCC), and extracellular polymeric substances (EPS) concentration for the developed biofilms under phosphorus restricted (P-restricted) and dosed (P-dosed) conditions. For both carbon concentrations, P-restricted conditions (≤0.3 μg P·L) limited bacterial growth (lower values of ATP, TCC). A faster pressure drop increase was observed for P-restricted conditions compared to P-dosed conditions when 250 μg C·L was dosed. This faster pressure drop increase can be explained by a higher area covered by biofilm in the flow channel and a higher amount of produced EPS. Conversely, a slower pressure drop increase was observed for P-restricted conditions compared to P-dosed conditions when 30 μg C·L was dosed. Results of this study demonstrate that P-limitation delayed biofilm formation effectively when combined with low assimilable organic carbon concentration and thereby, lengthening the overall membrane system performance.
营养限制是反渗透（RO）膜系统中的一种生物垢控制策略。在海水中，可供细菌生长的可同化有机碳含量范围约为 50 至 400μg C·L，而磷浓度范围为 3 至 11μg P·L。几项研究监测了生物垢的发展，限制了碳或磷的含量。碳磷比的影响以及两种营养物质对膜系统性能的限制尚未得到研究。本研究考察了降低磷浓度（从 25μg P·L 和 3μg P·L 降低至低浓度≤0.3μg P·L），同时结合两种不同的碳浓度（250μg C·L 和 30μg C·L）对 RO 系统中生物膜发展的影响。通过测量进料通道压降来确定所形成的生物膜对系统性能的影响。通过光学相干断层扫描（OCT）对两种碳浓度下积累的生物量的形态进行了表征，并通过测量总有机碳（TOC）、三磷酸腺苷（ATP）、总细胞计数（TCC）和胞外聚合物物质（EPS）浓度来量化所形成的生物膜的生物量和组成在磷限制（P 限制）和投加（P 投加）条件下。对于两种碳浓度，P 限制条件（≤0.3μg P·L）限制了细菌的生长（ATP、TCC 值较低）。当投加 250μg C·L 时，与 P 投加条件相比，P 限制条件下观察到更快的压降增加。这种更快的压降增加可以通过流道中生物膜覆盖的面积更大和产生的 EPS 量更多来解释。相反，当投加 30μg C·L 时，与 P 投加条件相比，P 限制条件下观察到较慢的压降增加。本研究的结果表明，当与低可同化有机碳浓度结合使用时，磷限制有效地延迟了生物膜的形成，从而延长了整个膜系统的性能。
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